While it would be great if you could get Carl Crawford or even Hanley Ramirez at a significant discount - and at this point you probably should - you're far more likely to make a profit on players about whom no one - including you - has any idea if they'll bounce back.
Here are a few I'd be looking to acquire in all but the shallowest of formats:
Buy Lower
Adam Dunn - he might come at 80-90 cents on the dollar, but at his age, and in that park, it's worth paying full price, no matter what the stats to date say. There are many possible causes for his struggles, but few are likely to be irreversible.
Dan Uggla - See Dunn, Adam. It's unlikely Uggla has ceased to be the player he was the last several years.
Mat Latos - The Ks are there, but the walks are higher, and he's giving up more home runs, despite his favorable home park. Latos' velocity is also down about 1.5 mph from last year, and he struggled with a shoulder injury early in the year. Nonetheless, Latos is the kind of pitcher who can carry your team when he's right, and pitchers don't always give advance warning before they find their grooves.
Billy Butler - Six homers and 34 RBI isn't cutting it from your first baseman nearly halfway through the year, but the Royals' lineup is no longer terrible, and Butler is the rare player who can be counted on to hit for average these days without costing you a star in return.
Aubrey Huff - His contract all but guarantees his presence in the lineup, and he's a career .283 hitter with 25-HR power.
Alex Rios - While the unseasonably cold Chicago weather didn't seem to affect Paul Konerko or Carlos Quentin, the White Sox' base stealers, Rios and Juan Pierre, have struggled so far. While manager Ozzie Guillen has cut back on the running aggressiveness, expect that policy to be temporary. Rios is also a .281 career hitter that's eclipsed the 20-HR mark twice.
Buy Lowest:
Chone Figgins - Figgins' .188/.235/.252 line is about halfway between your typical league-worst major league regular and a man on the street plucked at random to face big-league pitching. It's gotten so bad that Figgins has been relegated to the bench, despite receiving $9 million per year (and being signed through 2013). But while the Mariners have prospect Dustin Ackley at second, and all-world defender Brendan Ryan at short, journeyman Adam Kennedy, Figgins' replacement at third, is not the long-term solution. If Figgins - after a suitable break - gets into a groove, he'll be a middle-infield eligible player that can lead the league the AL in steals over the season's last couple months
Phil Hughes - He hasn't been the same since the first half of last year, but he's rehabbing, albeit with inconsistent velocity, and aiming to return to a team with as much run support as the league has to offer. Hughes did touch 95 on the gun during his rehab, and he's still a 25-year old formerly elite prospect.
Juan Pierre - For God knows what reason, Pierre hasn't lost his left field job yet, and that's despite being caught on nine of his 19 steal attempts. At this point, Pierre is a liability in every phase of the game, but as long as Ozzie Guillen still trots him out there, there's hope. Hope that he hits an empty .300 and starts running more successfully, once Guillen loosens the reins again on the bathpaths.
Rajai Davis - Like Pierre, Davis is a speedster whose lack of real-life offensive skills constantly threatens to relegate him to fourth-OF/pinch runner duty. But until Davis loses the job - and he might not until after the year - he's always got a chance to slap a few base hits and steal a ton of bases.
Domonic Brown - A .292 OBP doesn't sound very good, but it is when you have a .208 batting average. Brown has walked 13 times vs. 15 strikeouts, so it's not like he's overmatched, and he has four homers and two steals in 32 games. Maybe the Phils want to get Ben Francisco more involved again, or maybe they'll acquire another right-hand hitting outfielder at the deadline. But just as easily, Brown could get hot, establish himself and never look back.
Dexter Fowler - Charlie Blackmon has the job for now, but he's by no means entrenched as the left fielder of the future. A good run by Fowler at Triple-A, and a slump by Blackmon could reverse their situations in a week or two. Fowler struggled early on before getting hurt, but he draws walks, can handle center field and at least in theory steal bases (he was caught six times in eight attempts so far this year).
Derrek Lee - When you consider what aging formerly elite hitters like Lance Berkman, Travis Hafner and Todd Helton have been able to do now that they're healthy, you have to wonder whether players like Lee - himself just 35 - might follow suit. As recently as 2009, Lee went .306/.393/.579, and in 2005, he had an MVP-caliber .335/.418/.662 year. Can someone that good simply lose all of his skills a couple years later, or might they simply be masked by age-related injuries. It's worth acquiring Lee for a meager cost to find out.
Magglio Ordonez - He's finally back from his ankle injury, and he's hitting a little bit. See Lee, Derrek for why you might want to gamble on Ordonez, who just last year went .303/.378/.474.
Vernon Wells - The plate discipline has gone to the dogs, and he's not really capable of playing center field any more. But Wells has nine homers, two steals and a big enough contract to stay in the lineup. Don't expect more than a .260 batting average the rest of the way, but you could get 15 homers.
Brian Matusz - His velocity is down, and no one knows why. Like Matusz, Brandon Beachy returned from an oblique injury, and he's apparently fine. Maybe Matusz is seriously hurt and goes under the knife, but it's worth rolling the dice to see if what he needs is simply a mechanical fix. Matusz was lights out down the stretch last year, and he was one of the league's top pitching prospects heading into 2010.
Brandon Belt - He's already taking batting practice and after a sufficient rehab should be back in the majors - provided he shows he's fully healthy. He's one of the top hitting prospects in all of baseball. Gamble on the talent.