ORCHARD PARK, N.Y. — As if the Buffalo offense wasn’t anemic enough already, now it’s being thinned by injuries.

Tight end Charles Clay is out indefinitely after having arthroscopic surgery on his left knee, coach Sean McDermott announced Monday, a day after the team’s top receiving threat was hurt in a 20-16 loss at Cincinnati .

McDermott was unable to provide a specific timetable on Clay’s recovery except to say he’ll miss “multiple weeks.” Clay was hurt while being tackled along the sideline after making a 24-yard catch in the first quarter against the Bengals.

Clay, who leads Buffalo with 258 yards receiving, has accounted for three of the Bills’ five longest plays of the season.

His injury deals Buffalo’s offense yet another significant blow with starting receiver Jordan Matthews already sidelined indefinitely by a broken right thumb. Clay and Matthews have combined for 420 yards receiving and three touchdowns for a team that’s managed 910 yards and six touchdowns receiving through five games.

“Next man up,” was McDermott’s response to how the Bills move forward on an offense that lacked experienced depth to begin with.

And yet McDermott did acknowledge the offense will be his main concern with the Bills (3-2) heading into their bye week before returning to host Tampa Bay on Oct. 22.

“It’s a big priority,” he said.

Buffalo is down to four healthy receivers , with fifth-year player Andre Holmes having the most experience. At tight end, the trio of Nick O’Leary, Khari Lee and converted quarterback Logan Thomas began this season with a combined 11 catches for 158 yards.

The Bills’ LeSean McCoy-led running attack hasn’t been bowling over opponents either. After leading the NFL in yards rushing in each of the past two seasons, Buffalo ranks 16th with 533 yards rushing, and 28th in averaging 3.4 yards per carry.

The Bills haven’t topped 300 yards offense in each of their past four games, their most unproductive run since a seven-game stretch of sub-300-yard outings in 2009. They’ve scored just seven touchdowns, and are having difficulty finishing drives.

The troubles were particularly apparent against the Bengals . Buffalo managed 36 yards offense in the second half and was held to a field goal on two drives that began inside the Bengals 40.

The Bills went backward and were forced to punt after Jordan Poyer’s interception of Andy Dalton’s pass put Buffalo at the Bengals 36 early in the third quarter.

In the fourth quarter, Brandon Tate’s 40-yard punt return coupled with an unsportsmanlike conduct penalty gave Buffalo the ball at the Cincinnati 12. The Bills managed 2 yards before settling for Stephen Hauschka’s 28-yard field goal to cut the Bengals’ lead to 17-16 with 8:59 remaining.

“Those have to be opportunities for us where we cash in,” McDermott said. “And we didn’t do a good job of that yesterday.”

The struggles on offense overshadow how well the defense has performed under McDermott, who replaced Rex Ryan. Buffalo has allowed six touchdowns, is yet to give up more than 20 points in a game and has forced 10 turnovers, including three against the Bengals.

Quarterback Tyrod Taylor blamed himself.

“I’ll take full responsibility for that one,” Taylor said following the game. “The defense did a great job of getting us the ball back, but on offense we laid an egg.”

NOTES: Bills players are getting the entire week off and don’t return to practice until Oct. 16. … McDermott listed Matthews and starting cornerback E.J. Gaines (groin) as being week to week. … Backup CB Leonard Johnson is listed day to day after he hurt his hamstring on Sunday.


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