FLOWERY BRANCH, Ga. -- Atlanta Falcons coach Mike Smith said starting left tackle Sam Baker will undergo surgery on his left knee and be placed on season-ending injured reserve.

Baker returned from the injury two weeks ago but was back on the sideline for Sunday's 33-10 loss to the Seattle Seahawks. He was inactive for five games this season and seemed to aggravate the injury during a Week 4 loss to the New England Patriots.

"The medical people say that he needs to have the procedure done, so we're going to have that done," Smith said of Baker, although the coach didn't specify the date of surgery.

With the loss of Baker, Lamar Holmes will be counted upon to perform well at left tackle.

Smith talked about the expectations for Holmes with Baker out.

"I think Lamar has progressed extremely well at left tackle," Smith said. "I think he's gotten better every week."

The Falcons on Wednesday also signed veteran tackle Sean Locklear. As reported by ESPN.com on Tuesday, the Falcons had worked out Locklear along with fellow veteran tackle Rashad Butler.

Locklear, 32, is a former third-round draft pick of Seattle out of North Carolina State. He last played for the New York Giants and has 92 starts in nine seasons with the Seahawks, Washington Redskins, and Giants. He started all 19 games during Seattle's 2005 Super Bowl season.

In other news, the Falcons activated linebacker Sean Weatherspoon from injured reserve. He had been sidelined since suffering a Lisfranc foot sprain in a Week 2 win over the St. Louis Rams.

To make room for Weatherspoon on the roster, the Falcons released veteran linebacker Thomas Howard.