Carmelo Anthony repeated several times Saturday that Andrea Bargnani’s transformation as a defensive-minded Knick won’t “happen overnight.’’ However, Knicks coach Mike Woodson said he won’t wait a long time for the 7-foot Italian to make it as full-time starting power forward.

If he has to change the big frontline of Tyson Chandler, Bargnani and Anthony by Wednesday’s season opener against Milwaukee, Woodson will. The obvious change would be to send Bargnani to the bench for small forward Metta World Peace.

Bargnani, who celebrated his 28th birthday Saturday, is smack in his prime, but nobody feels he has hit his prime.

“I’ll experiment with [the big frontcourt], but I’ve got options this year,’’ Woodson said. “I can always go small, with Melo at the 4 with small teams and throw Bargnani in there when we got big teams. It’s not a matter of who starts, it’s what you do with the minutes that you’re in there. That’s the message I’m sending everybody on the team. You got to give productive minutes on the floor if you want to play.’’
Bargnani’s preseason was disappointing after a very sharp opener. He finished a minus in the plus-minus category in each of the last six preseason games — totaling a minus-72. He still is learning both the offensive and defensive systems, Woodson said.

Bargnani hasn’t been a good rim protector or rebounder in his career, and he extended that reputation this October.

“It’s not going to happen overnight,’’ Anthony said. “We had a preseason together. He’s still getting his feet wet as far as adjusting to New York. He’s still trying to adjust to New York. On the court with us, he’s still trying to adjust to that and we’re still trying to adjust to him.’’

Bargnani played seven seasons with Toronto and is amid his first NBA change. In addition, Bargnani is coming off pneumonia that had him bed-ridden for a month in late summer. His conditioning is still an issue.

“I still got to get better. Thirty days without doing anything, I haven’t had that in my life,’’ Bargnani said.