I agree its better to get a starter thru trade or free agency in the offseason. Much better.
While we may not need a 5th starter in the postseason, we may need a 4th starter in the later rounds, otherwise we are going to ask people to pitch on 3 days rest.
Right now, that 4th starter is CJ Wilson, who is good, at his best, for like 5 innings 3 ER. I keep having flashbacks to him giving up that 3 run bomb to Fielder in the 2011 all star game, promptly losing home field advantage for the rangers in the WS.