This is a frustrating situation. Neither has really been stealing many bases lately (3 for Roberts over the last month, 2 for Hairston). I've been playing Hairston over Roberts because his batting average has been better:
Roberts: .257 for the season, .260 over the last month;
Hairston: .299 for the season, .264 over the last month;
Roberts was great until Hairston came back. Hairston gets moved up and down the lineup. I hate to say it, but the best thing that could probably happen for either of them is for the other to either get traded or go on the DL for the remainder of the season. Then they'd have some certainty about their role, and be able to get into a routine.
"The game has a cleanness. If you do a good job, the numbers say so. You don't have to ask anyone or play politics. You don't have to wait for the reviews." - Sandy Koufax