The first day of the rest of a young football life will start one week from today in a place called Lambeau Field, against a quarterback named Brett Favre.

The Jets’ three-horse free safety derby became a two-horse race when the

club terminated the contract of journeyman vet Omar Stoutmire on the cutdown to 53.

One young colt is named Scott Frost.

The other young colt is named Kevin Williams.

As of yesterday, Al Groh was playing the exacta, still rotating Frost and Williams in practice and revealing nothing to the parties involved or to me and you.

The smart money says bet on Frosty The Groh Man.

Here’s what Williams has going for him: He has fashioned a miraculous comeback, from the death bed to the gridiron, and has considerably more upside than Stoutmire. So he has the kind of heart and mental toughness that Groh craves. But after a year away from the game, a year when he was stricken with a rare viral infection that settled in his throat and lungs and left him sedated for 14 straight days on a respirator and a 158-pound weakling, Groh might not be so inclined to throw him to the wolf, aka Favre, when the games begin to count.

Here’s what Frost has going for him: In his put-up-or-shut-up summer, he has put up. He has overcome a much lesser adversity: the difficult transition from quarterback at Nebraska to quarterback of the defense in the NFL. When Bill Parcells and Dick Haley drafted the 6-2, 220-pound specimen in the third round in 1998, just before they selected Williams, they envisioned Carnell Lake. Frost sank before he swam.

“I felt like I was a fish out of water,” he said. “I’d been doing one thing practically my whole life, and then I was trying to be something else at a level where you have to be able to perform at the highest level to be able to compete, and it was really frustrating for me to come in some days and feel like I was starting to get it, and you come in other days and feel like I was still miles away from where I needed to be.”

There was a time when the mere sight of, say, Tommy Maddox would have terrified Frost. Not even Favre can scare him now. Frost, who has all of six career tackles and two passes defensed as a sub DB, was asked yesterday whether Favre might be licking his chops at the sight of him in the Jets secondary. “I don’t think licking his chops; I hope not,” Frost said. “If they’re gonna throw it my way, I’m gonna make some plays. That’s the way I gotta look at. You know anytime there’s a young guy in the secondary I think other teams might have a tendency to game-plan toward him a little bit, but you just gotta be ready for that challenge.”

He thinks he has made his greatest strides in man-to- man coverage, and was heartened by the change from Bill Belichick to aides Todd Bowles and Mike Nolan. “Coach Bowles has helped me a ton with technique,” Frost said. “Coach Nolan’s helped me a lot with my eyes and being able to see things. I’m just glad that Al’s had a lot of confidence in me this year.”

Al sure does.

“He’s certainly come a long ways; I guess the frost has thawed here of late,” Groh said. “I’d say he’s come a long ways since January. His performance from that point – offseason program, spring workouts, summer training, through training camp – has demonstrated an awareness on his part that this was it. That the foundation, if there was one, had been laid, and now it was time to see where his career was gonna go.”

What kind of things has Frost showed you? “Aggressiveness,” Groh began. “Very good concentration throughout the course of practice; he’s kept his attention on what he knew he had to accomplish from the outset. Not just participating but very resolute in his efforts. Improved his strength considerably, dropped weight, much more aggressive tackler, which was one of the things that was a little difficult for him in the beginning coming from quarterback. I think one, learning how to do it and two, finding out that it didn’t really hurt … all the time.”

Williams, you may recall, started in his first game as a rookie against Steve Young, and before long was watching Jerome Henderson and Corwin Brown, who gave way last year to Steve Atwater, who gave way to Stoutmire. The 6-0, 190- pounder started six games that season.

“He certainly is a lot more field-aware player than he was as a rookie,” Groh said.

Williams couldn’t agree more. “I think that I’ve gotten wiser,” he said.

He feels like his old self again. “Since the doctors released me [Feb. 4], I haven’t had any problem doing anything,” Williams said.

Now they wait. “Kevin and I have been here together for two years already, we’re gonna be here together again,” Frost said. “However they divvy up the responsibility, we’re gonna do it the best we can.”

Williams: “That’s their decision and they’ll make the decision. I’m just trying to do what I can do and I just let God take care of the rest.”