CLEARWATER, Fla. — There is a certain humility required for a 35-year-old man and his right arm that has fired 39,431 regular-season pitches. Roy Halladay now admits this reality, one he either neglected or was unwilling to accept. No one, even the most prepared, is immune to mortality.

"Hopefully I'm not sitting here anytime soon and saying I'm done playing," Halladay said Wednesday. "That's a big thing in this game: You never want to look back and wish you had done something different."

So Halladay says he has changed it all to survive as long as possible. His rigorous routine, the stuff of spring legends, is totally different from when he arrives to Bright House Field at the crack of dawn. His throwing is altered. His conditioning program is new.

Not surprisingly, his confidence is unwavering.

"There is no such thing as a crystal ball," Halladay said. "But I'm confident that if I can maintain the way I feel right now that I'm going to be effective."

In his first public comments since last season ended, he cited a previously undisclosed lower back injury that led to shoulder problems and one of the worst years in his storied career. Halladay claimed he did not reveal that injury because he did not know exactly what the cause was.

He spent six weeks on the disabled list with a strained muscle in the rear of his shoulder. Usually, that is a problematic area for pitchers. The Phillies long stressed there were no structural red flags contained in multiple examinations of Halladay's shoulder. The back injury lends credence to that theory.

Doubt is natural. For months, Halladay hid his ailments despite signs suggesting distress.

"I feel as good now as I have in any other spring training," Halladay said. "Last year, it's not that I felt bad, it just never seemed to click for me. The longer it got into the season, I could never really solve the problems I was having. It made it tough."

The two-time Cy Young Award winner reiterated his desire to finish his career with the Phillies. Halladay will be a free agent at season's end. He has not opened dialog with the Phillies about a contract extension, nor does he expect to.

The Phillies, likewise, will want to wait and see if electricity remains in Halladay's great right arm before committing millions to it.

"I'm playing to win a World Series," he said. "If I had my druthers, I would be here until I am done."

If he regains his ace form, the Phillies are likely to share those feelings.

Contact Matt Gelb at mgelb@phillynews.com or follow on Twitter @magelb.