The 2017 baseball season came to an end Wednesday night when the Houston Astros beat the Los Angeles Dodgers in a surprisingly anticlimactic Game 7 of the World Series. It is the first championship in Astros history.

Baseball is a year-round sport, of course, and the offseason started Thursday with 149 players becoming free agents at 9 a.m. ET. The MLB Players Association released the free-agent list Thursday. Here are all the important dates you need to know this offseason, and here is a breakdown of each club's free-agent class.

Arizona Diamondbacks

Martinez, clearly, is the big fish for the Diamondbacks. He was superb after coming over at the trade deadline, and surely the D-Backs would love to find a way to keep him in their lineup going forward. They figure to have to win a nine-figure bidding war to make that happen, however.

Atlanta Braves

Small free agent class for the Braves. Dickey, who had his $8 million option declined earlier this week, hinted at retirement at the end of the regular season. 

Baltimore Orioles

The Orioles are shedding three starting pitchers who combined to throw 287 1/3 innings with a 7.17 ERA in 2017. Yikes. Hellickson, Jimenez, and Tillman combined to make approximately $29 million while throwing those 287 1/3 innings, so, on the bright side, the O's are unloading three expensive and ineffective pitchers.

Boston Red Sox

Earlier Thursday the Red Sox made two no-brainer decisions when they exercised their club options for Chris Sale and Craig Kimbrel. They weren't letting those guys get away, obviously. The Red Sox will have to replace -- or re-sign -- Fister, Moreland, Nunez and Reed, all of whom held down important-ish roles in 2017.

Chicago Cubs

The Cubs are losing two starting pitchers and their closer, in addition to several valuable role players. They are not expected to get into a bidding war for either Arrieta or Davis, so it'll be interesting to see how their address their pitching staff next season. At times this year, and especially in the postseason, their lack of reliable pitching depth was exposed.

Chicago White Sox

Any impending free agents with value were traded by the rebuilding White Sox at the deadline. They're not expected to be big spenders in free agency, though they could grab a few reclamation projects and hope to cash them in as trade chips at the 2018 deadline.

Cincinnati Reds

Cozart is, by a fairly significant margin, the best free agent shortstop this offseason. The Reds chose not to trade him at the deadline, so I'm curious to see whether they make an effort to re-sign him over the winter. Even though they're rebuilding, Cincinnati needs quality veterans to help the young guys find their way, and a good two-way shortstop like Cozart will always have trade value.

Cleveland Indians

The Indians could potentially have another key player hit the open market this winter: Michael Brantley. The club holds an $11 million club option for Brantley for next season -- the option includes a $1 million buyout, so it's essentially a $10 million decision -- and while he was productive in 2017, he had ankle surgery last month and is expected to need at least five months to recover before resuming baseball activities. He may not return to the field until May. In that case, the club may not want to tie up a relatively significant chunk of payroll on a player who's battled serious injuries the last two years.

Colorado Rockies

Greg Holland is expected to decline his $15 million player option in the coming days, allowing him to become a free agent as well. In Holland, McGee, and Neshek, the Rockies are faced with the possibility of losing their three best relief pitchers to free agency this offseason. They'll have some work to do to rebuild that relief core.

Detroit Tigers

Similar to the White Sox, the Tigers traded just about all of their impending free agents prior to the trade deadline. Sanchez had his $16 million club option unsurprisingly declined last month.

Houston Astros

The World Series champion Astros had five players hit the open market Thursday, though none of the five are core players. Even Beltran was limited to pinch-hitting duty in the postseason. He may retire now that he's finally won a ring. Houston is not losing a single player who was crucial to their World Series success on the field.

Kansas City Royals

No team has a larger free agent class in terms of impact players than the Royals. Their starting shortstop (Escobar), starting first baseman (Hosmer), starting third baseman (Moustakas) and starting center fielder (Cain) are all free agents. So is an All-Star pitcher (Vargas). The Royals knew this was coming, of course. They chose to keep the band together at the trade deadline and make one last run at the postseason. Admirable, though it didn't work. 

Los Angeles Angels

The Angels handled maybe their most important piece of offseason business Thursday morning, when they signed Justin Upton to a new five-year contract worth $106 million. Upton could have opted out of the four years and $88 million left on his contract and tested the free agent waters. The Halos essentially gave him a one-year extension worth $18 million to not opt out.

Los Angeles Dodgers

Two weeks ago, re-signing Darvish seems like a very real possibility for the Dodgers. Now, after two disastrous World Series starts in which he recorded 10 outs total, it seems like Darvish and the Dodgers will part ways. Morrow, meanwhile, went from afterthought last offseason to a potentially big payday this offseason. He was fantastic in relief for Los Angeles from start to finish, with only a few hiccups along the way.

Miami Marlins

The Marlins are reportedly planning to slash payroll this offseason, and they're not going to get much help from their group of free agents. Among those three free agents, Ellis was the highest paid in 2017 at $2.5 million.

Milwaukee Brewers

Garza's four-year stint with the Brewers was very up-and-down. There were a lot of injuries mixed in as well. It's difficult to see Milwaukee bringing him back. The club figures to try to retain Swarzak and Walker, two trade deadline pickups, however.

Minnesota Twins

The Twins sold at the trade deadline this year, remember. They moved their prominent impending free agents at July 31 only to rally in the second half and qualify for the postseason as a wild card team. Belisle, Colon, and Gee were useful depth arms this summer. Chances are the Twinkies will look to add a little more impact to their pitching staff now that they know their young core is ready to contend.

New York Mets

Just the one free agent for the Mets. Reyes played this season at the major league minimum because the Rockies still owed him $22 million after releasing him last year. The Mets, remember, traded away just about all of their notable impending free agents at the deadline, including Granderson, Walker, Bruce, and Reed.

New York Yankees

Masahiro Tanaka has until Saturday to decide whether to opt out of the final three years and $67 million left on his contract. He had a tough regular season this year (4.74 ERA), though a fantastic postseason (0.90 ERA in three starts) could be enough to help him land more money on the open market, even if he takes a smaller average annual value. Tanaka could also try to leverage his opt-out clause into an extension from the Yankees a la Upton and the Angels.

Oakland Athletics

  • None

No free agents for the Athletics, who made some deals at the deadline to unload their notable players set to hit the open market. 

Philadelphia Phillies

The Phillies have shed just about all of their large contracts over the last few years, so they'll move forward as a rebuilding team with a ton of payroll flexibility. Don't be surprised if they made a big splash in free agency this winter, or take on an onerous contract in a trade.

Pittsburgh Pirates

A few weeks ago Jaso hinted at retirement because he wants to sail around the world in his boat. Sounds like a fun retirement plan. The Pirates are not poised to lose any key players to free agency this winter.

San Diego Padres

Very quietly, Stammen had an excellent season for the Padres, throwing 80 1/3 innings with a 3.14 ERA. It was his first extended MLB action since 2014. He could be a nice little middle relief target for some team this winter.

San Francisco Giants

The big name here is Cain, the longtime rotation stalwart who announced his retirement at the end of the season. With Johnny Cueto not expected to opt out of the final four years and $92 million remaining on his contract, the Giants are shedding a big salary in Cain ($21 million) and not much else.

Seattle Mariners

The Mariners declined their club options for Gallardo and Iwakuma earlier on Thursday. Aside from Iwakuma (injuries) and Beckham (September call-up), Seattle is losing players who had defined roles in 2017. Dyson was their starting center fielder, Alonso and Valencia platooned at first base, Gallardo was mostly in the rotation, and Ruiz provided veteran leadership as the backup catcher. The club has some roster holes to fill this winter.

St. Louis Cardinals

Four pretty important pitchers are hitting the open market for the Cardinals. Lynn was in the rotation all year, Oh was the closer much of the last two years, Nicasio was the closer this September, and Duke was the middle innings left-on-left matchup guy. St. Louis is loaded with young arms, however, so they don't figure to be desperate to re-sign any of these four free agents.

Tampa Bay Rays

The Rays added Cishek, Duda, and Romo at the trade deadline in hopes of making a push for a postseason spot, though they fell short. Cobb is their big name here. He shook off the rust following Tommy John surgery this year and was steady and reliable, throwing 179 1/3 innings with a 3.66 ERA. Cobb will be a popular target among teams looking to add a quality starting pitcher without spending Arrieta/Darvish money.

Texas Rangers

Cashner quietly threw 166 2/3 innings with a 3.40 ERA this season -- his 4.6 WAR placed in the top 10 among AL pitchers -- so he's poised to land a nice contract this winter. He bet on himself with a one-year deal worth $10 million in 2017, and he was able to rebuild value. It'll be interesting to see whether the Rangers make him the $17.4 million qualifying offer.

Toronto Blue Jays

Once the Blue Jays officially decline their half of Jose Bautista's $17 million mutual option, he will become a free agent as well. It'll be weird seeing Joey Bats in a uniform other than Toronto's, assuming he hooks on elsewhere despite serious signs of decline in his game.

Washington Nationals

No team has a larger free agent class than the Nationals, who had 11 players hit the open market Thursday. That includes close to a full bullpen worth of relievers, as well as Werth, whose seven-year contract worth $126 million has expired. The Nationals are desperate to win right now, in 2018, before Bryce Harper and Daniel Murphy become free agents next winter. They figure to be very aggressive in free agency, as always.