Yankees and Mets fans were gnashing their teeth as Scott Kazmir scorched his way through the Bombers’ lineup yesterday afternoon.

Kazmir, the former Mets first-round pick they traded to Tampa Bay for Victor Zambrano last year, turned in arguably the best start of his young career in a 5-3 Devil Rays win at the Stadium.

“He’s pitched good baseball against a lot of teams,” Tampa Bay manager Lou Piniella said of the 21-year-old lefty. “He’s learning. He’s learning on the job. Since spring training, he’s improved a lot. He needs to keep getting better, get more economical with his pitches, learn to soften up his fastball at times to get an easier out, but that comes with experience.

“That doesn’t come at a young age,” Piniella said. “But since spring training, this young man has gotten better and better.”

Kazmir yesterday allowed four hits over seven innings with four strikeouts against a lineup that devastated the Devil Rays in a 13-run eighth inning less than 24 hours before he took the hill.

“I was kind of joking with teammates, saying they got all their hits out [Tuesday] night,” Kazmir said. “But I wasn’t worried about that at all. I was just concentrating on my game.”

It was solid from the start, save for a mistake pitch to Gary Sheffield that landed in the left-field seats 12 throws into the outing. But Kazmir settled down, retired the next 11 batters he faced, and the little lefty was zipping fastballs in the high 90s late into the afternoon.

When he got himself in trouble in the sixth by loading the bases with a pair of walks (one intentional) and a single, Kazmir ended the frame by getting Russ Johnson to pop out.

“There was probably a lot more adrenaline going,” Kazmir (3-5) said. “It was my first time pitching at Yankee Stadium, so there were a little bit of jitters at the beginning.”

Kazmir is a player who may haunt the Mets for years after they moved him a day before last summer’s trade deadline. Instead of rubbing salt in that wound yesterday, he was diplomatic and said he doesn’t think much about the Mets.

“I couldn’t have planned this out any better. I’m in a great situation,” Kazmir said. “I’m very happy where I’m at.”

Here in New York, there are others who continue to pull out their hair because of where he’s at.