Josh Rosen will be trading Bruins blue for Big Blue, according to Mel Kiper’s first mock draft.

The long-time ESPN draft expert has the Giants drafting the strong-armed Rosen at No. 2 after — somewhat surprisingly — he has the Browns drafting Wyoming quarterback Josh Allen at No. 1.

“Rosen is the top pure passer in this class,” Kiper opined. “He looked better than Darnold when UCLA and USC played late in the season. Rosen, however, has dealt with injuries the past two seasons, and there already have been rumblings that he doesn’t want to end up in Cleveland.

“There are some red flags. But some team is going to draft him high — he has rare arm talent and has been much more secure with the ball than [Sam] Darnold and Allen. The Giants could move into life after Eli Manning with a new franchise quarterback.”

It’s been widely speculated that the Giants will draft Manning’s successor with this pick after last year’s third-rounder Davis Webb did not find his way to the field, despite the team’s dismal 3-13 season and a brief benching of Manning for second-stringer Geno Smith.

The Jets’ draft quarterback position is more in doubt with the No. 6 pick and largely depends on what the teams in front of them do. In Kiper’s mock, the Jets would miss out on the top three prospects with the Broncos taking Darnold at No. 5. The Jets would then turn to Alabama star Minkah Fitzpatrick, according to Kiper.

“Fitzpatrick is the top cornerback and safety in this draft,” Kiper wrote. “He could play either position. He was primarily a safety at Alabama, but he covered receivers in the slot and on the outside, and he consistently made plays.

“New York took safeties with its top two picks last year (Jamal Adams and Marcus Maye), so Fitzpatrick would be a corner for the Jets, who have an opening with Morris Claiborne a free agent this offseason. This is another spot to watch for one of the top quarterbacks.”

Indeed, if the Broncos go in another direction — they still have 2016 first-rounder Paxton Lynch on the roster — that could allow the Jets to take the last signal-caller standing from the consensus top three.

Kiper’s mock, though, does lay out an interesting quarterback scenario for the Jets. It has the Redskins taking Oklahoma’s Heisman-winning quarterback Baker Mayfield at No. 13. While that’s certainly no lock it does underscore that Kirk Cousins’ future is up in the air this offseason.

Cousins has been franchise-tagged by Washington two seasons in a row and a divorce is possible this offseason. The Jets are expected to have approximately $100 million in cap space and are in desperate need for a quarterback of the future with Bryce Petty and Christian Hackenberg looking less and less like the answer with each passing season. And the idea of using a veteran bridge quarterback for a fourth straight season — two years of Ryan Fitzpatrick, one of Josh McCown — is not overly appealing to a frustrated fan base.