The buy-low, sell-high mantra is one of the most overused in fantasy sports. No one in any league worth playing in will deal you Carl Crawford, Kevin Youkilis or Carlos Gonzalez at a discount just because of two bad weeks. In order to get an actual bargain then, you need to target players whose market values have declined since draft day for good reason and about whom even you are worried. While buying low usually isn't possible, buying lowest typically is.
Here are a few players I'd target in AL- or NL-only leagues, or deeper mixed ones:
Phil Hughes - He's on the DL due to ineffectiveness and diminished velocity, and he fell off significantly in the second half last year. But we're still talking about a one-time elite pitching prospect that was one of the better starters in the American League during 2010's first half. Last year Max Scherzer was in a similar boat, got sent down to the minors and returned excellent value in the second half.
Javy Vazquez - Vazquez was one of baseball's best starters in 2009, but flopped in his second stint with the Yankees last year, and like Hughes, lost speed on his fastball. His slow start in Florida has only lowered his stock further, and he should be available for next to nothing in all but the deepest of leagues.
Joe Nathan - Nathan's been so bad since returning from Tommy John surgery he's already lost his job. But some rust was to be expected, and given his stature and track record in the Twins organization, I think it's only a matter of time before he reclaims the closer role ? provided he pitches well in a set-up capacity.
Domonic Brown - One of the game's elite hitting prospects, Brown broke his wrist in spring training and rendered moot the question of whether he'd emerge ahead of Ben Francisco as the Phillies' third outfielder out of camp. Brown flopped in a 62 at-bat audition with the team late last year, but let's not forget he had 20 homers, 17 steals and a .327 batting average in 343 high-minors at-bats as a 22-year old. As soon as Brown proves he's healthy by tearing up Triple-A, the team will make room for him. Francisco is a decent replacement-level fill-in, but he's not nearly valuable enough to block a prospect of Brown's caliber on a contending team.
Chone Figgins - Figgins started off slowly last year, too, but rebounded in the second half and finished with 42 steals for the second straight season. With three years and $27 million left on his contract, it's hard to see the team sending him to the bench any time soon, and given Figgins' .143 batting average on balls in play and 89 percent contact rate, his roto stats should normalize before too long.
Derrek Lee - It's easy to forget Lee posted a .306/.393/.579 line just two years ago, and while he's been dogged by thumb, wrist and foot injuries over his last couple hundred at-bats, Lee should still have plenty left in the tank at age 35 provided he gets healthy.
Carlos Pena - The .196 batting average last year shows you his downside, but even so, he hit 28 homers in 144 games playing in the AL's best pitcher's park. He's dealing with a thumb injury right now, but once he gets healthy, he's a 35-40 homer threat at Wrigley Field.
Austin Jackson - Last year's .399 batting average on balls in play portended regression, but let's not overdo it. Jackson's only 24, stole successfully on 27 of his 33 attempts and plays elite centerfield defense, something which virtually assures his presence in the lineup. His .175 average early on should reduce his price tag sufficiently.