The Ravens will be shorthanded at tight end for Sunday's game against the Cincinnati Bengals as veteran tight end Owen Daniels underwent arthroscopic surgery on his left knee after his injury didn't improve this week.
Daniels was officially ruled out on the injury report.
Rookie tight end Crockett Gillmore will start in place of the two-time Pro Bowl selection.
"As the week went on, his knee was not really progressing the way we wanted it to," Ravens coach John Harbaugh said of Daniels. "We went ahead and did a cleanup procedure and he'll be out for this game. After that, he actually has a chance to come back.
"It will kind of be week to week after that, and it won't be many weeks at all. It could actually be next week. That'd be an optimistic approach, but it could happen."
Daniels wasn't limping in the locker room Thursday, the same day offensive coordinator Gary Kubiak downplayed his injury.
"Owen is fine," Kubiak said. "John [Harbaugh] has a plan for these veteran guys. I know he has had a plan for O.D. and how he keeps him fresh and keeps him ready to go. As far as what we're doing, game plan, those type of things, O.D. will be fine."
Daniels favored his knee during the second half of a 29-7 win over the Atlanta Falcons last Sunday, consulting with trainer Mark Smith but remained in the game.
The Ravens have relied heavily on Daniels ever since tight end Dennis Pitta's season-ending hip injury. Daniels has caught 27 passes for 275 yards and three touchdowns.
Now, they'll need a greater contribution from Gillmore. The third-round draft pick from Colorado State has caught three passes for 29 yards.
"He's going to be ready," Harbaugh said of Gillmore. "He had a great week of practice. He's done a heck of a job."
Gillmore has played in every game , increasing his workload to 43 snaps against the Falcons when he caught one pass for 13 yards. This will be his first NFL start.
"I've prepared to be the guy since the first day I was here," Gillmore said. "I've been following around those guys, Owen and Dennis. So, they've given me a great opportunity to step in their shoes and do what I can do. I'm next man up. I'm going to just keep blocking and help out the passing game."
The Ravens could also have former Green Bay Packers tight end Ryan Taylor active Sunday. Another option is to have 6-foot-5, 214-pound wide receiver Marlon Brown active as a red-zone threat after he was a healthy scratch last week.
"Ryan is a good athlete, really smart," Harbaugh said. "All the things he did in Green Bay, you see him doing here. He can really run, good hands, lead blocker type guy."