BEREA, Ohio (AP) — The Browns have some major holes to fill on defense.

Cleveland lost starting linebacker Christian Kirksey and cornerback E.J. Gaines for the season after placing both on injured reserve.

One of the team’s captains, Kirksey hurt his hamstring in the second quarter of Sunday’s 37-21 loss to the Kansas City Chiefs. Gaines sustained his second concussion in three weeks when he took a knee to the helmet while trying to make a tackle in the first quarter.

The losses will make things even tougher on a Cleveland defense already stretched thin.

Linebacker Joe Schobert, a 2017 Pro Bowler, missed the past three games with a hamstring injury, rookie cornerback Denzel Ward hurt his hip against the Chiefs, and cornerback Terrance Mitchell broke his arm earlier this season.

Schobert returned to practice Wednesday, as did cornerback Damarious Randall, who was kept out Sunday with a nagging groin injury. Ward and linebacker Jamie Collins were limited to riding stationary bikes during the portion of practice open to media members.

Kirksey made 43 tackles and two interceptions in seven starts.

Gaines, who signed with Cleveland as a free agent in March, moved into the starting lineup after Mitchell went down. He made one interception.

The Browns signed defensive back Juston Burris to the active roster off the New York Jets’ practice squad.

Cleveland takes a four-game losing streak into Sunday’s game against Atlanta.