I think we need a clarification of sorts.

We've reached the point this season when players start to develop track records within the season itself, so when you hear someone talk about changes in a player's value, they might just mean from one week to the next.

But not me. I don't reset until March 2009.

OK, I wouldn't go that far, but when I talk about players' Fantasy appeal sliding up or down, I generally use opening day as a starting point. To avoid getting caught up in streaks, I try to identify permanent changes in players, and in most cases, I need more than a week or two to decide.

So the week a player goes in this column is the week I make up my mind on him. Each of the players listed here did something in the last week to "seal the deal," in a way. I could just as easily list Carlos Quentin, I suppose, but he sealed the deal for me long ago.

Obviously, opening-day value loses all relevance at some point, and when that point comes, I'll let you know. We'll be in on it together -- like buddies, except you much angrier and oblivious to punctuation.

So there you have it: my role, your role and everything else you need to know to enjoy the latest edition of Fantasy Sliders.

Sliders

These guys' recent performances signify more than a hot or cold streak. Their Fantasy appeal has actually "slid" either up or down.

Kevin Youkilis, 1B, Red Sox

I chastised a friend in a mixed league for taking Youkilis as his starting first baseman. He has since become my bitter enemy.

And you know what? I deserve it. Since that fateful draft, our teams have gone opposite directions -- his, the way of glory and, mine, down the toilet with more force than a Carlos Pena swing-and-a-miss.

Leave it to the Greek God of Walks to walk all over me.

I know Youkilis hitting five home runs this past week was crazy -- so crazy he'll probably never do it again -- but he had impressed me even before the craziness. Home runs aside, he has increased his extra-base hits, decreased his strikeouts and maintained a batting average over .300.

Don't forget his .288 batting average last year would have looked much better had he not hit .238 in the second half. And as for the increase in homers, age 29 isn't too late for a power breakout, especially considering Youkilis didn't become an everyday player until age 27.

I don't think he'll maintain his current pace of 32 home runs, but I wouldn't count him out for 25 with a batting average over .300 and a league-leading walk total. At this point, I'd rather have him than Todd Helton and, depending on the format, maybe even Pena.

Victor Martinez, C, Indians

Never has a .346 batting average meant so little in Fantasy.

I don't think anyone would knock the pursuit of a batting title, but when you draft the No. 1 catcher, you expect him to hit a few homers. So far, Martinez has none, and the season is nearly one-fourth over.

I don't mean to say he won't hit any because he obviously will. But his struggles now afford me the opportunity to say that we in the Fantasy industry have overrated him for quite some time now. We call him a power hitter, but his 25 long balls last year set a career high. He hit 16 the year before -- a number that would probably disappoint Chris Snyder this year -- and has only once slugged over .500. Not to mention his status as the No. 1 catcher isn't such a slam dunk anymore with Russell Martin, Brian McCann and Geovany Soto all knocking on his front door.

For the record, I don't mean to say you should sell low on V-Mart. He'll get better before he gets worse. But you clearly don't have that edge at catcher you thought you did when you drafted him in the third round.

Ervin Santana, SP, Angels

Santana always had one thing going for him: He could pitch well at home.

But that ability made him only half credible in Fantasy and half useful to the Angels, and as the difference in performance became more pronounced over the years, Santana found himself spending more time in the minor leagues and less in the hearts and minds of Fantasy owners. By this spring, he had become a late-round afterthought, his few backward-minded believers uttering something about winter ball statistics.

But a crazy thing happened this weekend. Santana threw a shutout ... on the road.

It means something, and even though he followed that shutout with a shaky performance at Tampa Bay, his 3.44 ERA on the road suggests he's made the necessary adjustments. Combine it with his 1.31 ERA at home, and you have a dang good Fantasy pitcher -- possibly the makings of an ace.

Aaron Hill, 2B, Blue Jays

On second thought, saying Hill had a power breakout last season was a little premature.

His 17 home runs far exceeded his six from the year before, and he had never hit more than 11 in the minors. Plus, he hit five of those 17 in April, slugging not much higher than his current .390 the rest of the way.

A slump has caused his stats to suffer this year, contributing to a .262 batting average that has, in turn, limited his opportunities to hit home runs. But given his track record, you probably shouldn't hold out hope for more than double digits anyway.

Ryan Ludwick, OF, Cardinals

Hold those e-mails about how I neglected to name an NL player this time. Take your finger off the send key. I found one in Ludwick.

But nobody else did, not in our 20-team office league known as "The B.I.G.S.," where we have an AL-only side and an NL-only side. I happen to play on the AL-only side, and when I went to pick up a free-agent outfielder one day, forced to weigh the pros and cons of such fan favorites as Frank Catalanotto and Shannon Stewart, there he was, staring at me from the top of the list -- mocking me, taunting me.

This went on for about two weeks. It actually made me angry.

Let me ask you something: If you see a player with a .347 batting average and eight home runs through the middle of May, forget your Fantasy team, right? You might consider voting him into the All-Star game. So how does Ludwick go unclaimed in an NL-only league? It doesn't make sense.

Fortunately, all that changed this glorious Monday morning. When I woke up to discover someone had claimed Ludwick, I threw a little party in my PJs.

Don't get me wrong. Ludwick won't sustain his batting average, and he won't belong in the All-Star game by the time it actually gets here. His peripherals and track record say so. But I have no doubt his power is legitimate, and if he has the ability to hit 30 home runs, doesn't he belong on most mixed-league rosters, much less NL-only? If nothing else, I think he's convinced the Cardinals he deserves the most at-bats in an outfield rotation with Chris Duncan and Skip Schumaker.

Hanging Sliders

These guys look like Sliders, but not so fast! Their recent performances might cause you to misinterpret their Fantasy appeal.

George Sherrill, RP, Orioles

Including Sherrill here might almost sound like a contradiction after my glowing recommendation of Brian Wilson last week, but allow me to highlight the differences:

1) The Orioles are .500 right now. They won't finish .500. If they do, I'll buy you an ice cream.

2) The Orioles don't have near the starting pitching of the Giants. Daniel Cabrera looks like their ace, but his control issues still surface from time to time. And unless you think Jeremy Guthrie and Brian Burres can maintain their combined 3.98 ERA, the Orioles have a black hole after him.

3) The Orioles actually do have some decent hitters. Nick Markakis is an emerging All-Star. Brian Roberts is already there. Kevin Millar and Aubrey Huff at least make their families proud. So on the rare occasion the Orioles win, they might win by too much to give Sherrill a save situation.

So sell Sherrill's 13 saves while you still have a chance. He might finish with 30 just because he can't lose what he already has, but his pace should slow dramatically.

Blake DeWitt, 3B, Dodgers

I admit I started to develop a liking for DeWitt. He had a 1-to-1 strikeout-to-walk ratio, a starting job all to himself with Nomar Garciaparra and Andy LaRoche sidelined, and after a 9-for-21 week, a .323 batting average. But then I took a closer look at his minor-league numbers and started to feel a little uncomfortable about recommending him.

In short, I don't think the plate discipline will continue. In anything close to a full season in the minors, his highest on-base percentage was .339, which, if you're keeping score at home, is not good. If the plate discipline doesn't continue, the batting average won't continue. And we already figured DeWitt's power wouldn't develop until later.

Of course, some players just hit better in the majors, and DeWitt certainly wouldn't be the first to figure out the strike zone after his arrival. But if I had to guess today, I'd say DeWitt will be little more than decent in Fantasy -- worth using in NL-only leagues, but prone to losing his job to La Roche down the road.

Aaron Cook, SP, Rockies

Cook has a 6-1 record. He has a 1.13 WHIP. He has a 2.26 ERA, including a 1.47 mark over his last five starts, and is the hottest thing off the waiver wire since Nate McLouth in Week 1.

So why do I smell Kent Bottenfield from here all the way to St. Louis?

OK, so maybe Cook is a little better than Bottenfield, the Cardinals' out-of-nowhere 18-game winner in 1999, but he still is the very embodiment of mediocrity, having posted a 4.31 ERA and 1.45 WHIP in 115 career starts. How he would suddenly become a Fantasy ace with his uninspiring track record is beyond me. And with a strikeout rate of fewer than one every two innings, you know some of those batted balls have to start dropping into play at some point.

I wouldn't blame you for taking a flier on Cook while he's hot, but I don't credit his performance so far as anything more than a prolonged good start.

Change-up

Every week, I make terrible errors in judgment. It happens to us all, and if it didn't, Fantasy wouldn't be a game worth playing. Fortunately, I permit myself the opportunity to correct one of my mistakes by throwing a change-up.

Jonathan Sanchez, SP, Giants

Some people might call for me to insert Fausto Carmona here after he threw a five-hit shutout Monday, and that would certainly make sense considering I talked about him last week. But I refuse to budge. His walk rate still scares me.

Which is exactly why I turn back the calendar a couple of weeks to my assessment of Sanchez. After he completed his second 10-strikeout game, I gushed over him like a school girl who had just gotten her hand held. But in three starts since then, my enthusiasm has waned. He has a 7.53 ERA and a 1.95 WHIP, averaging about 4 2/3 innings per start, and is in serious jeopardy of falling out of mixed-league relevance.

Any pitcher who strikes out more than a batter per inning deserves an extra look, but if Sanchez has one more shaky start without showing me something good, I'll probably give him the ax.

You can e-mail Scott your Fantasy Baseball questions to dmfantasybaseball@cbs.com. Be sure to put Attn: Sliders in the subject field. Please include your full name, hometown and state.We'll answer as many as we can.