From new coach to old guard

Zimmer talked this summer about how many NFL head coaches don't get much time to grow into the job, and he had a point: Of the six head coaches who broke in with Zimmer in 2014, three already have been fired by their teams while the remaining four already are tied for the 13th-longest tenures of any active NFL coach. Here's a look at the NFL Coaching Class of 2014 through three seasons:

Bill O'Brien, Houston: Three 9-7 seasons and one win in three playoff games.

Regular-season record: 27-21

Jim Caldwell, Detroit: Records of 11-5, 7-9 and 9-7. Lions lost both playoff games.

Regular-season record: 27-21

Mike Zimmer, Vikings: Records of 7-9, 11-5 and 8-8. Lost only playoff game.

Regular-season record: 26-22

Jay Gruden, Washington: Followed 4-12 first season with 9-7 and 8-7-1 records.

Regular-season record: 21-26-1

Mike Pettine, Cleveland: Started 7-9 but was fired after a 3-13 second season.

Regular-season record: 10-22

Lovie Smith, Tampa Bay: Went 6-10 after a two-win first season but was fired.

Regular-season record: 8-24

Ken Whisenhunt, Tennessee: Fired after the seventh game of his second season.

Regular-season record: 3-20