SANTA CLARA -- During his introductory press conference in January, Chip Kelly was asked if there was merit to the criticism that his fast-paced offensive system put too great a burden on his defenses.
Kelly responded by saying it was the defense's responsibility to get off the field as quickly as possible and minimize its own snaps.
"I’ve never met a defense player that says, ‘Coach, I want you to possess the ball for the entire game so I don’t have to play,'" he said. "I want guys that on the defensive side of the football of the San Francisco 49ers can’t wait to get on the field and embrace the opportunity to get out there and play. And when you have a bunch of guys like that, it doesn’t matter."
Fourteen weeks into the season, however, the 49ers' defenders probably could use a break.
Sign Up and Save
Get six months of free digital access to The Sacramento Bee
They've played an NFL-high 959 snaps so far and on Sunday were noticeably fatigued in the fourth quarter and overtime. Safety Antoine Bethea couldn't wrap up a Jets receiver, who after a catch gained another nine yards to the San Francisco 15-yard line. On the same drive, outside linebacker Ahmad Brooks couldn't take down running back Bilal Powell before he scored a touchdown then had trouble stopping quarterback Bryce Petty on the ensuing two-point conversion.
Of Powell's 145 rushing yards, 121 came after halftime against a defense that, with three games to go, nearly has played the equivalent of a full season.
Kelly acknowledged after Sunday's game that his defense had worn down by the end. But he said that the unit is not fatigued overall. "I think that's one thing (you see) when you look at the tape -- these guys play with great effort," Kelly said.
He also noted that he has slowed his famously frenetic pace on offense to the point where the quarterback usually snaps the ball with single digits left on the play clock, unheard of when he coached at the University of Oregon and rare during his previous three seasons with the Philadelphia Eagles.
"It's not like we're playing fast football right now," he said on Monday. "We're not converting (first downs) when we need to convert."
The 49ers rank 27th in the league in converting 3rd downs to first downs, doing so at a 35. 2 percent rate. Their 78 punts this season rank second to the Rams' 79 punts. Los Angeles fired its head coach, Jeff Fisher, on Monday, one day after the Rams fell 42-14 at home to the Atlanta Falcons.
Kelly noted that the 49ers' early scores against the Jets came quickly -- after a takeaway deep in New York territory and after the 49ers picked up big chunks of yardage on their second offensive possession. The two touchdowns were scored in 1:56.
For all their rushing yardage -- 248 total -- the 49ers didn't string together any long, methodical drives and held the ball for only 24:30 as opposed to 41:55 by the Jets. The 49ers converted only one of seven third downs -- 14 percent.
"We need to stay on the field offensively," he said. "That's the biggest thing. We need to convert and keep drives alive."
McDonald on IR -- Three days after they signed Vance McDonald to a five-year contract extension, the 49ers placed the tight end on injured reserve with a shoulder injury. McDonald played 17 snaps Sunday before suffering the injury. Blake Bell filled in for the last three quarters.
The 49ers filled McDonald’s spot by signing offensive lineman Josh Allen, who recently was with Tampa Bay. Allen can play center and presumably would be a backup to Marcus Martin while Daniel Kilgore is coming back from a knee injury suffered Sunday.