Rex Ryan can't be happy about this.

Former Jets defensive coordinator Mike Pettine, Ryan's right-hand man for four seasons, was hired by the Bills for the same position, ESPN's Chris Mortensen reported Wednesday morning.

Ryan and Pettine agreed to part ways. Pettine's contract with the Jets has expired; he declined an extension at the start of the season.

In Tuesday's news conference, Ryan acknowledged the obvious, that Pettine was moving on, but he didn't want him to land in Buffalo.

"I'm hoping he doesn't take that job," Ryan said, half-jokingly. "I'm hoping he goes somewhere else. We've had conversations, and right now Mike thinks it's best that he goes to a different team as a defensive coordinator, and I wish him all the best -- unless he goes to Buffalo."

Four quick thoughts on this move:

1. Let's be clear: Ryan is the mastermind of the Jets' defense, but this move isn't a good thing because his defensive playbook will now be in the hands of a division rival. Of course, it works both ways -- the Jets will have a great feel for the Bills' scheme -- but I think the Bills get the edge in that trade-off. Until the season finale, the Jets had been ripping through the Bills' defense for several years.

2. You could see a few Jets players surfacing in Buffalo. DT Mike DeVito, S Yeremiah Bell and S LaRon Landry will be unrestricted free agents. LBs Bart Scott and Calvin Pace and S Eric Smith will be salary-cap casualties, meaning they, too, will be available.

3. This is a great hire by new Bills coach Doug Marrone, who likes to play an attacking, blitz-heavy defense. He'll get that style from Pettine, and he stole a small piece of Ryan's brain in the process.

4. The Jets will make a seamless transition, promoting secondary coach Dennis Thurman to coordinator.