You can tell when the calendar is about to change months early in the baseball season. The prospect chatter always seems to increase and the transaction report gets a bit longer.

May 1 is upon us and some prospects are pushing for a pre-June arrival. We quickly break down the top 10 prospect newsmakers this week, hoping this scatter-like shotgun spray will hit some of the surprise arrivals this weekend -- or more realistically in the next 10 days to two weeks.

1. Starlin Castro, SS, Cubs (15 percent owned)

A report on ESPNChicago.com says "Castro's ascension to the major leagues could be right around the corner, according to a major league source." The fact Castro is just 20 years old makes us believe nothing is as imminent as that source might think. We will call that story bunk and far too speculative, even if it excites us in the prospect rat-race. The Cubs are ready to shake things up, moving ace Carlos Zambrano to the bullpen, but they would have to move Ryan Theriot to second base to slot the raw talent in the majors amid a pennant race. That would be a dicey and drastic move, albeit far more logical than Big Z in a setup role. Castro is hitting a ridiculous .370 with a homer, 18 RBI, 15 runs, four steals, .416 OBP and .593 SLUG. He doesn't walk much at all, but he has only struck out nine times in Double-A in 81 at-bats, a good sign he isn't overmatched. His ownership needs to rocket upward on CBSSports.com, even if it is more likely he is promoted to Triple-A soon rather than the major leagues.

2. Chris Tillman, SP, Orioles (19 percent owned)

When you throw a no-hitter and the big club is temporarily going with a four-man rotation, Fantasy owners tend to jump on the bandwagon. Tillman won't be the call-up for Saturday's No. 5 starter's slot, but he could position himself for an arrival a few turns later. You don't get any more impressive than the no-hitter he pitched Wednesday, walking one and striking out six. He needed just 105 pitches, perhaps the only reason he was allowed to go the distance.

3. Michael Stanton, OF, Marlins (26 percent owned)

The Marlins said they needed to see Stanton dominate Double-A before he could be moved up. He struggled there in 2009, hitting just .231 with 99 strikeouts in 299 at-bats after being moved up from high Class A. This week he popped off with five homers in two games (six in four), forcing the organization to answer some questions about when he might arrive. "Two good days in a row are not going to influence our decision," said Jim Fleming, the Marlins' assistant GM and vice president for player development. "It's (all about) at-bats over time. We need a consistent pattern and he has been pretty consistent, but those two days are just that." For the season, Stanton is hitting .338 with nine homers, 22 RBI, 20 runs, a .489 OBP and .789 SLUG. Interestingly, he has walked 20 times and struck out 19 in 71 at-bats -- a much better ratio. He is too good for Double-A right now, so perhaps a move to Triple-A New Orleans could come soon. Chris Coghlan's sophomore struggles suggest a 2010 arrival is possible, too.

4. Buster Posey, C, Giants (45 percent owned)

There have been discussions in the organization about promoting Posey before June, according to the San Francisco Chronicle. We don't see how they could do that with veteran Bengie Molina hitting .350, but they could slot Posey as a super utility man. He was versatile at Florida State, playing all nine positions in his final game there. The fact Posey could arrive and not play regularly at catcher actually hurts his Fantasy value some. Keeper leagues that need players to stay off the active roster in order to be retained on prospects lists might actually hope he stays down.

5. Stephen Strasburg, SP, Nationals (86 percent owned)

OK, we tried to bury the lede but couldn't resist mentioning this name. Unlike Tillman, Strasburg is being held to a tight pitch count in Double-A, going five perfect innings, striking out six Tuesday night. Strasburg's ERA sits at 0.52 and his batting-average against is .115 through 17 1/3 innings. Clearly, he is ready to move, but a promotion to Triple-A will come first. "As he progresses, he is going to go to (Triple-A) Syracuse and is going to pitch there until we deem he is ready to go to the next level," GM Mike Rizzo said. "It's reasonable to assume he is going to be in Syracuse sometime soon." They have already announced he will start Sunday in Double-A, so a move to Triple-A seems likely after that game.

6. Aroldis Chapman, SP, Reds (74 percent owned)

Chapman is already in Triple-A, stretching out to a career-high six innings in start No. 4 on Wednesday night. Through 21 innings, he has struck out 22 and allowed a mere .192 batting-average against. We said five or six starts and 25-30 innings before a call-up. By this time next week, we could be anticipating an imminent arrival. Aaron Harang got his act together in his past start, so Bronson Arroyo, Johnny Cueto and Homer Bailey have the spotlight on themselves their next time out.

7. Carlos Santana, C, Indians (40 percent owned)

We listed the struggling early-season major leaguers who were looking over their shoulder at elite prospects in Triple-A. Of that group, Ike Davis and Justin Smoak arrived shortly after. No. 1 on that top five list was Santana. He still waits. Lou Marson has picked up the production the past couple of days, but Marson's production won't matter once the Indians decide to pull the trigger on Santana. "People ask all the time, 'When are you going to The Show?'" Santana told the Akron Beacon Journal this week. "I just say, 'I'm working here. I'm working to get better. Soon.'" His manager Mike Sarbaugh says: "The consensus has always been [that] his bat's already there; it's just being consistent defensively game to game."

8. Jake Arrieta, SP, Orioles (13 percent owned)

We already figure Brad Bergesen is a done deal for Saturday, but Arrieta is just as worthy of a call-up. He has allowed runs in only one of his four starts this season, posting a 0.36 ERA and .157 batting-average against, striking out 25 in 23 innings. Those are Strasburg-quality numbers. Arrieta could still be held back a few days to make his debut Saturday but do we really need him to be the Orioles' No. 5 starter? How about making Jeremy Guthrie a closer, or David Hernandez a reliever?

9. Trevor Cahill, SP, Athletics (17 percent owned)

For all the disappointment in Brett Anderson's elbow issue, we do get a silver lining: Cahill could get his 2010 rotation shot. We figure he gets the call over Vin Mazzaro as the A's temporary Anderson fill-in. If Cahill pitches well, he will stick around long term and prove worthy of being added even in mixed leagues. He might not have Anderson's knockout stuff, but he is a quality young arm that is more wise beyond his years (innings) than most.

10. Brad Bergesen, SP, Orioles (6 percent owned)

OK, so he's already been around this season, but the fact he will get the recall before the no-hit author Tillman and red-hot Arrieta makes him newsworthy. We slot him 10th on this list because he is the least likely to hold value in mixed leagues, even if he will be the first to arrive Saturday. Bergesen is not helped any by pitching for the Orioles right now, a team that had the embarrassing distinction of having half as many victories as baseball's lowest total. The Orioles had just four wins before play Thursday, while the Royals, White Sox, Braves, Astros and Dodgers were tied for the next-lowest at eight. Ew.

Prospect watch

Every week we break down all the minor leaguers who are owned in at least 1 percent of our Fantasy leagues. This will be your essential guide to unearthing the elite prospects before they hit the big time.

CBSSports.com's most-owned minor leaguers
Player POS TM Own% Player POS TM Own% Player POS TM Own%
Stephen Strasburg SP WAS 86 Ben Revere CF MIN 3 Greg Halman RF SEA 1
Aroldis Chapman SP CIN 74 Andrew Cashner SP CHC 3 Chris Nelson SS COL 1
Buster Posey C SF 45 Juan Francisco 3B CIN 3 Henry A. Rodriguez RP OAK 1
Carlos Santana C CLE 40 Josh Reddick LF BOS 3 A.J. Pollock CF ARI 1
Chris Iannetta C COL 36 Chris Heisey CF CIN 3 Andrew J. Carpenter SP PHI 1
Pedro Alvarez 3B PIT 30 Chris Withrow SP LA 3 Alexander Colome SP TB 1
Chris Davis 1B TEX 29 Jeff Samardzija RP CHC 3 Bobby Borchering 3B ARI 1
Madison Bumgarner SP SF 26 Emilio Bonifacio 3B FLA 3 Hak-Ju Lee SS CHC 1
Michael Stanton RF FLA 26 Chris Marrero LF WAS 3 Daniel McCutchen SP PIT 1
Desmond Jennings CF TB 24 Jaff Decker OF SD 3 Jason Donald SS CLE 1
Brett Wallace 3B TOR 19 Hector Rondon SP CLE 3 Jeremy Jeffress SP MIL 1
Chris Tillman SP BAL 19 Tony Sanchez C PIT 2 Michael Pineda P SEA 1
Jeremy Hellickson SP TB 18 Brandon McCarthy SP TEX 2 Angel Villalona 3B SF 1
Kyle Drabek SP TOR 17 Alex White SP CLE 2 Joe Savery SP PHI 1
Jesus Montero C NYY 17 Ethan Martin SP LA 2 Chris C. Carter LF NYM 1
Trevor Cahill SP OAK 17 Adeiny Hechavarria SS TOR 2 Roger Kieschnick LF SF 1
Jarrod Saltalamacchia C TEX 17 Wilson Ramos C MIN 2 Noel Arguelles SP KC 1
Chris C. Carter 1B OAK 16 James Darnell 3B SD 2 Logan Forsythe 3B SD 1
Starlin Castro SS CHC 15 Josh Lindblom SP LA 2 Lance Lynn SP STL 1
Drew Storen RP WAS 14 Jemile Weeks 2B OAK 2 Chuck Lofgren SP MIL 1
Domonic Brown RF PHI 13 Simon Castro SP SD 2 Kam Mickolio RP BAL 1
Jake Arrieta SP BAL 13 Mike Minor SP ATL 2 Dellin Betances SP NYY 1
Michael Taylor LF OAK 12 Hank Conger C ANA 2 Zack Wheeler SP SF 1
Dustin Ackley 1B SEA 12 Nick Hagadone SP CLE 2 Matt Maloney SP CIN 1
Martin Perez SP TEX 10 Zach Britton SP BAL 2 Mark Rogers SP MIL 1
Logan Morrison 1B FLA 10 Scott Elbert RP LA 2 Ryan Strieby 1B DET 1
Fernando Martinez OF NYM 9 Danny Valencia 3B MIN 2 Troy Patton SP BAL 1
Christian Friedrich SP COL 9 Mike Trout CF ANA 2 Sean O'Sullivan SP ANA 1
Daniel Hudson SP CHW 9 Jason Knapp SP CLE 2 Kevin Pucetas SP SF 1
Yonder Alonso 1B CIN 8 Adrian Cardenas SS OAK 2 Esmil Rogers SP COL 1
Michael Brantley CF CLE 8 Nick Weglarz RF CLE 2 Josh D. Fields RP SEA 1
Derek Holland SP TEX 8 Beau Mills 1B CLE 2 Rick VandenHurk SP FLA 1
Casey Kelly SP BOS 8 Trevor Reckling RP ANA 2 Tyson Gillies RF PHI 1
Jason Castro C HOU 8 Brad Lincoln SP PIT 2 David Purcey SP TOR 1
Josh Bell 3B BAL 7 Jeanmar Gomez SP CLE 2 Wilin Rosario C COL 1
Tim Beckham SS TB 7 Miguel Sano SS MIN 2 Josh Thole C NYM 1
Freddie Freeman 1B ATL 7 Brett Jackson CF CHC 2 Ivan DeJesus SS LA 1
Tyler Flowers C CHW 7 Jose Iglesias SS BOS 2 Jess Todd RP CLE 1
Mike Aviles SS KC 7 Sean West SP FLA 2 Austin Romine C NYY 1
Tommy Hunter SP TEX 7 Thomas Neal LF SF 2 Matt Sweeney 3B TB 1
Mike Moustakas 3B KC 6 Zach Stewart SP TOR 2 Chad James SP FLA 1
Jarrod Parker SP ARI 6 Kila Ka'aihue DH KC 2 William Myers C KC 1
Brad Bergesen SP BAL 6 Jordan Walden SP ANA 2 Shairon Martis SP WAS 1
Jack Cust LF OAK 6 Jared Mitchell CF CHW 2 Adam Miller SP CLE 1
Jacob Turner SP DET 6 Travis Wood SP CIN 2 Zach McAllister SP NYY 1
Josh Vitters 3B CHC 6 Alex Liddi 3B SEA 2 Neil Walker 3B PIT 1
Lars Anderson 1B BOS 5 Mike Jacobs 1B NYM 2 Vin Mazzaro SP OAK 1
Aaron Crow SP KC 5 Matt Antonelli 2B SD 2 Matthew Hobgood SP BAL 1
Lonnie Chisenhall 3B CLE 5 Jake McGee SP TB 2 Conor M. Gillaspie 3B SF 1
Brett Lawrie 2B MIL 5 Kyle Gibson SP MIN 2 Andrew Lambo LF LA 1
Todd Frazier OF CIN 5 Arodys Vizcaino SP ATL 2 Peter Bourjos CF ANA 1
Taylor Teagarden C TEX 5 James McDonald RP LA 2 Donnie Veal RP PIT 1
Phillippe Aumont SP PHI 5 Jordan Lyles SP HOU 2 David Cooper 1B TOR 1
Dee Gordon SS LA 5 Trevor May SP PHI 1 Wes Hodges 3B CLE 1
Tyler Matzek SP COL 5 Will Inman SP SD 1 Angel Salome C MIL 1
Michael Bowden RP BOS 5 Danny Cortes SP SEA 1 Jay Jackson SP CHC 1
Michael Montgomery SP KC 5 William Rowell 3B BAL 1 Chris Valaika SS CIN 1
Brandon Allen 1B ARI 5 Wilkin Ramirez LF DET 1 Andrew Brackman SP NYY 1
Aaron Hicks OF MIN 5 Hector Gomez SS COL 1 Travis D'Arnaud C TOR 1
Timothy Alderson SP PIT 5 Kyle Skipworth C FLA 1 Josh Anderson CF CIN 1
Carlos Carrasco SP CLE 5 Jiovanni Mier SS HOU 1 Gorkys Hernandez CF PIT 1
Dayan Viciedo 3B CHW 4 Rich J. Hill SP STL 1 Allen Craig RF STL 1
Tanner Scheppers SP TEX 4 Christian Bethancourt C ATL 1 Michael Main SP TEX 1
J.P. Arencibia C TOR 4 Brandon Snyder 1B BAL 1 Deolis Guerra SP MIN 1
Julio Teheran SP ATL 4 Daniel Espinosa SS WAS 1 Casey Weathers RP COL 1
Eric Hosmer 1B KC 4 Daniel Schlereth RP DET 1 Glen Perkins SP MIN 1
Michael Saunders LF SEA 4 Micah Hoffpauir 1B CHC 1 Daryl Jones CF STL 1
Casey Crosby SP DET 4 Aaron Cunningham RF SD 1 Fautino De Los Santos RP OAK 1
Hank Blalock 1B TB 4 Ruben Tejada SS NYM 1 Brandon Erbe SP BAL 1
Donovan Tate CF SD 4 Wladimir Balentien LF CIN 1 Brad Mills SP TOR 1
Derek Norris C WAS 4 Michael Burgess RF WAS 1 Scott Lewis SP CLE 1
Matt Moore SP TB 4 Jordan Danks CF CHW 1 Bryan D. Anderson C STL 1
Michael Ynoa SP OAK 3 Craig Kimbrel RP ATL 1 Engel Beltre CF TEX 1
Wilmer Flores SS NYM 3 Jonathan LuCroy C MIL 1 Jose Ceda RP FLA 1
Armando Galarraga SP DET 3 Anthony Slama RP MIN 1 Zach Braddock RP MIL 1
Ryan Westmoreland OF BOS 3 Kasey Kiker SP TEX 1 Reese Havens SS NYM 1
Andrew Miller SP FLA 3 Aaron Miller SP LA 1 Ryan Tucker SP FLA 1
Carlos Triunfel SS SEA 3 Bradley Holt SP NYM 1 Chad C. Jenkins SP TOR 1
Jose Tabata LF PIT 3 Steve Pearce 1B PIT 1 Anthony Rizzo 1B BOS 1
Aaron Poreda RP SD 3 Eric Arnett SP MIL 1 Anthony Swarzak SP MIN 1
Matt Dominguez 3B FLA 3 Mark Melancon RP NYY 1 Brent Morel 3B CHW 1
Grant Green SS OAK 3 Max Stassi C OAK 1 John Mayberry LF PHI 1
Shelby Miller SP STL 3 Ryan Kalish CF BOS 1 Mike Carp 1B SEA 1

Rookie watch

Top AL rookies to date

  1. Austin Jackson, OF, DET -- He is striking out once every three at-bats, but he is hitting, running and scoring.
  2. Wade Davis, SP, TB -- His mid-90s stuff is pretty impressive and makes him a must-own in all leagues now.
  3. Neftali Feliz, RP, TEX -- He has struggled more of late, but the Rangers are sticking with him at closer still.
  4. Brian Matusz, SP, BAL -- He looks capable of being a winner even with the lowly O's, but they hold him back.
  5. Reid Brignac, 2B, TB -- He has been far more consistent than Sean Rodriguez, which might earn him more time.

Top NL rookies to date

  1. Jaime Garcia, SP, STL -- He is looking like a must-own and must-start in all Fantasy leagues at this point.
  2. Mike Leake, SP, CIN -- Even we are surprised at how well he has held up without any minor league innings.
  3. Jason Heyward, OF, ATL -- He has hit his first extended slump, but he should come out of this very soon.
  4. Tyler Colvin, OF, CHC -- We didn't see him getting this many at-bats, or doing quite this much with them.
  5. Ike Davis, 1B, NYM -- He has hit the ground running with his gap power and run production through Week 1.

You can e-mail Emack your Fantasy Baseball prospect questions to DMFantasyBaseball@cbs.com. Be sure to put Prospects in the subject field. Please include your full name, hometown and state. Be aware, due to the large volume of submissions received, we cannot guarantee personal responses to all questions.