6:03 PM ET

OXNARD, California — Dallas Cowboys offensive lineman Marcus Martin needs surgery on his right big toe to repair a ligament tear suffered in the preseason opener against the San Francisco 49ers, sources told ESPN.

Martin, who signed a one-year deal with the Cowboys as a free agent in March, was competing for one of the backup interior offensive line spots. He missed a couple of days of practice to work on his conditioning, but the Cowboys believed he could play a role behind Travis Frederick, Zack Martin and Connor Williams.

The injury leaves the Cowboys with veteran Joe Looney, who has held the backup spot the past two seasons.

In 2016, La’el Collins, then playing left guard before his 2017 move to right tackle, suffered a similar injury and spent the final 13 regular-season games on injured reserve, although he was close to being able to return for the playoffs.

In other news for the Cowboys, weakside linebacker Sean Lee will take part in his first full practice of training camp. The Cowboys have worked Lee slowly into practice after he missed five games last season with two separate hamstring strains.

Lee has gone through walk-throughs

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