"Definitely, I would think I won't [start Sunday]," Pettitte told the Houston Chronicle for Tuesday's editions.
Pettitte last week had pleaded with manager Jimy Williams and general manager Gerry Hunsicker to keep him from going on the 15-day DL for the second time this season. But the team denied his request and, in what appears to have been the correct course of action, put the pitcher on the DL retroactive to May 27 due to a muscle injury.
"I think it was a good decision," Pettitte told the Chronicle. "Let's put it this way: It'd be stupid for me to go out right now if they think I have a strained muscle in my forearm. I did think I would progress a little bit quicker than I did. I thought I'd be long-tossing and put a lot more on it quicker than I have.
"I can sit here and say that I probably could have pitched, but realistically, I probably couldn't give us much."
Pettitte, who threw a light bullpen session for the first time Monday, won't put a revised timetable on his return. He expects to throw long toss Tuesday and a "good, hard bullpen" session Wednesday.
Pettitte has already missed two starts during this stay on the DL and will miss at least one more.
"First of all, there's just no way to predict how a player is going to recover from an injury," said Hunsicker, who wanted Pettitte on the DL so the pitcher would not rush back. "With Andy's case, the progress has been slow, but we seem to be heading in the right direction."