Mickens’ career, which has spanned 11 seasons, nine of which were with the Jets as one of the top nickel cornerbacks in the business, has taken him to New England, where he was signed as a free agent a month ago.

The reason for his cram session of studying is Sunday’s AFC wild-card showdown between his new team, the Patriots, and his former team, the Jets.

And, as Mickens knows well, having played for Eric Mangini before, preparing for a Mangini-coached team is as daunting as preparing for a Belichick-coached team.

Mickens conceded yesterday, in a conversation with The Post, that he couldn’t help but smile when he saw the playoff scenarios unfold Sunday and when the dust settled it was Jets-Patriots, 1 p.m. Sunday.

“Man, this is a big game,” he said. “I had a wonderful career with the Jets and that’s where it ends. I’m a New England Patriot now and I’m going to do everything I can to help the Patriots win.”

Mickens said he still has numerous friends in the Jets’ locker room with whom he speaks regularly. There hasn’t been and will not be any friendly phone conversations with former teammates this week, though.

“No, I stay away form that,” he said. “What I’ve got to do here, making sure I’m prepared, is more important than giving a friend a call this week.”

Despite the fact he was cut by the Jets on the last day of training camp this past summer, Mickens holds Mangini in high regard.

“I really don’t have any bad blood feelings about their decision,” Mickens insisted. “I shook hands with Eric and Mike (Tannenbaum, the GM) before I left.

“I felt like I was having a good camp coming back off sports hernia surgery. It was really just a decision to keep Derrick Strait, a younger guy. They did what they felt was best for the team, and obviously they’re in the playoffs so it worked out.”

Strait, of course, was jettisoned later.

Mickens went home to Dallas, worked out, stayed ready, and got a call from the Patriots’ Scott Pioli in early December.

Now Mickens will try to help beat the team he made his career with.

“I feel blessed to be up there, to be back with coach Belichick, the guy that helped my career substantially when I first started,” Mickens said. “He taught me how to be a professional. I played for him for three years (with the Jets) and I’ve carried those same standards with me even when he wasn’t my coach anymore. To be reunited with him is a blessing.”

Mickens recalled the days when Belichick was Jets defensive coordinator and the defensive players couldn’t wait to get to work on Wednesdays to see what kind of game plan he concocted for that week’s game.

“He was always doing something differently,” Mickens said.

There is a similar pattern going on with Mangini and his players. Mangini, like his mentor Belichick, is constantly shaking things up so no opponent can get a beat on any tendencies.

That is the most fascinating element to Sunday’s game: How Belichick counters the things Mangini was so successful with in the Jets’ 17-14 November victory in Foxborough, and how Mangini shakes things up this time.

Mickens, because of the combustible and sensitive nature of the complicated Belichick-Mangini relationship, steered clear of getting into too much analysis of the two.

“This week,” Mickens said politely, “I’m not going to be comparing those two guys. I’m not going to get into that. I have respect for Eric as well as the other (Jets) coaches. I respect Eric whole-heartedly.

“I told people the Jets were going to be successful with Eric as head coach. I believed Eric was going to get that thing turned around.”

The question is whether Mangini has the Jets turned around and good enough to overcome Belichick’s playoff-tested Patriots in their own building.

Mickens wouldn’t touch that topic either, but the feeling here is that the Mangini Jets do, indeed, have the stuff to beat the Belichick Patriots.

mark.cannizzaro@nypost.com