Keep an eye on hitters and pitchers LOPS & ROPS. This stat is available on your team page.

OPS is (OBA + SLG)

LOPS is vs. lefties
ROPS is vs. rightes

For hitters its how well they hit vs. a lefty or righty. The higher the better. Getting a guy in the .900+ range is very good. Since 3/4 of all pitchers are right handed, being better vs. righties for hitters is more important.

For pitchers its how well they pitch vs a lefty or a righty. For pitchers the lower the better. Getting below .700 is good.

The best pitcher might have a .690 vs both lefties and righties, but a pitcher that is a .650 vs. righties and .800 vs. lefties can still be effective, just match them up with favorable teams or individual hitters.