“Maybe we should have spent more,” Johnson said. “Probably should have.”

In contrast to two years ago, when Idzik replaced Mike Tannenbaum, the next general manager will enter an appealing situation, with more than $40 million in salary-cap space, the No. 6 pick in the draft and, most likely, a role in selecting the new coach. The search to fill both jobs has already begun, though Johnson said he would prefer hiring a general manager first.

Johnson, who will be guided by the former N.F.L. general managers Charley Casserly and Ron Wolf, has hired only coaches with defensive backgrounds: Herman Edwards, Eric Mangini and Ryan. With the Jets in need of someone to groom their next quarterback, whoever that may be, this time Johnson may prioritize offense. He praised Ryan repeatedly, but in detailing his criteria for the next coach — comprehensive oversight of offense, defense and special teams, not just one unit — Johnson identified a Ryan shortcoming.

Among N.F.L. assistants, potential candidates could include the Seattle defensive coordinator Dan Quinn, who will interview with the Jets in Seattle this week; the Arizona defensive coordinator Todd Bowles; the Cincinnati offensive coordinator Hue Jackson; the Detroit defensive coordinator Teryl Austin; and the Denver offensive coordinator Adam Gase. In the college ranks, Gus Malzahn of Auburn, Jim Mora of U.C.L.A. and Brian Kelly of Notre Dame could merit looks.

To replace Idzik, Johnson said he would hire an executive with vast experience in personnel. Contenders could include Chris Ballard, the Chiefs’ director of player personnel; Eric DeCosta, the assistant general manager of the Ravens and the apparent successor-in-waiting to his immediate boss Ozzie Newsome; George Paton, the Vikings’ assistant general manager; Lake Dawson, the Titans’ vice president for player personnel; Duke Tobin, the Bengals’ director of player personnel; Mike Maccagnan, the Texans’ director of college scouting; and Trent Kirchner, the Seahawks’ director of pro personnel.

“This is very, very critical right now,” Johnson said. “We’ve got to make some good decisions.”

Johnson thought he made a good decision when he hired Ryan, then the defensive coordinator in Baltimore. After endearing himself to fans and players with his audacious confidence and his insistence that the Jets — his Jets — would be feared for years to come, Ryan departs as a man humbled by his team’s downfall.

Counting the postseason, the Jets were 50-52 under Ryan, who is the only coach in franchise history to have guided the Jets to back-to-back appearances in the conference championship game. But he never reached the Super Bowl, nor did he ever dislodge the rival New England Patriots from atop the A.F.C. East. Ryan finished 4-9 against New England, including a victory in the 2010 playoffs, and 16-21 in the division, 1-5 this season.