DeJesus is only batting .262 with a .328 slugging percentage. He's got a good on base percentage (but not as good as Clevenger, Campana, LaHair, or Mather) and he hasn't stolen a base yet, but he has been caught stealing. He's a classic Cubs lead off man: when gets on, he simply stands around waiting for something to happen-- instead of making things happen.
Hitting .175, Stewart is simply a disaster. Plus the man has no history of being a good hitter at the majors. 63 AB already this year after playing practically everyday is enough to relegate him to the bench, IMO.
Signing Mather to a minor league contract was probably one of Theo's most fortunate moves. After a fantastic spring, Mather's currently hitting .286 with a .400 on base percentage-- even though Sveum has only allowed him to play sporadically.