Linebacker Jadeveon Clowney left Sunday's win in the second quarter with a knee injury and didn't return.
On Monday, head coach Bill O'Brien gave an update on the rookie's status.
"He underwent arthroscopic surgery this morning," O'Brien said. "He'll probably be out for about four to six weeks."
O'Brien also said it seemed like the surgery "went well".
The head coach also said the injury occurred on a second quarter play in which Clowney "jumped in the air and came down awkwardly". While the loss of Clowney is an obvious blow to the defense, O'Brien was quick to point out the reality of the situation.
"Injuries in this League occur all the time," O'Brien said. "Every team today is sitting here with injuries. That's just the nature of the game."
Clowney suffered a concussion during the week of practice in Denver, and missed the preseason games against the Broncos and 49ers. In June he had surgery for a sports hernia.
In Clowney's absence, third-year linebacker Whitney Mercilus filled the void. He registered two quarterback hits against Robert Griffin, III, and will be the starter at the "Jack" outside linebacker spot while Clowney is out.
O'Brien also said undrafted rookie Jason Ankrah, who was inactive on Sunday, will get an opportunity for playing time this week and in the near future.