Pettitte has been sidelined since last week, when he felt tightness in his lower back while driving home from Legends Field. He threw 47 tosses on flat ground on Monday and was scheduled to receive treatment on Tuesday before throwing a side session on Wednesday.
"I just want to be healthy now," Pettitte said. "Did I want to pitch game two? Of course I did. That's where they lined me up to pitch. The important thing for me right now is that I want to be healthy. If I miss a start, it's not the end of the world.
"I'm encouraged right now that they're not talking about skipping a turn. It's progressing, and I feel like I will start in that first series."
Manager Joe Girardi said that right-hander Mike Mussina will pitch in New York's second game of the season, making the April 2 start against the Blue Jays.
The rotation will now feature Chien-Ming Wang starting on Opening Day, followed by Mussina, then either Pettitte or Phil Hughes. Ian Kennedy, who starts on Tuesday at Winter Haven against the Indians, will be the fifth starter.
"Obviously, it's important that you have different looks," Girardi said. "Chien-Ming Wang is different than Moose, and Moose will be different than either Hughes or Andy. Hughes will be different than Kennedy. That's important to me."
Catcher Jorge Posada said that the team will have no difficulty in the early schedule as a result of pushing back Pettitte.
"It's much more important to have him healthy for later in the season," Posada said. "I think we'll be just fine. The young guys are throwing the ball really well right now. Moose is throwing well, Hughes is throwing well. That's all you can ask."
The tentative plan is to have Pettitte remain behind this weekend as the Yankees travel to Miami, allowing him to pitch in a Minor League game in Tampa on Saturday.
"Any time something like that releases and a guy starts feeling better, it makes you feel better," Girardi said. "Especially someone you're really counting on."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.