Claiborne, who did not play in the preseason opener because of tendinitis in his right knee, injured his right shoulder during Wednesday's practice with the Oakland Raiders. Coach Jason Garrett said Claiborne would not practice Thursday and probably won't play Saturday against the Baltimore Ravens.
"It's some kind of an AC joint separation, but we got good news about it yesterday, better than the initial reports thought it might be," Garrett said. "We think it's going to be more of a day-to-day, within-the-week type of thing."
Claiborne hasn't come close to living up to expectations since the Cowboys traded their top two picks to move up eight spots in the first round to draft him sixth overall in 2012. He has only two interceptions in two seasons and has struggled in coverage.
He's had his development stunted by several injuries during training camps. He has played in only two preseason games in his career.
"We'd rather have him out there," Garrett said. "You want him to take every rep, but sometimes these things happen. I do think he's become a better player because of the experiences that he's had over the first couple of years of his career.
"I think he's at a higher level now than he was last year at this time. Hopefully, he can get back from this thing as quickly as possible and take advantage of the last couple of weeks of the preseason."
Claiborne lost his starting job last year after missing the entire preseason due to a knee injury. He suffered an injury to his left shoulder in the regular-season opener and underwent offseason surgery after playing hurt all season.
Safety Matt Johnson, another oft-injured defensive back from the Cowboys' 2012 draft class, returned to Dallas on Thursday to visit a specialist in an attempt to determine if back problems are the cause of his chronic hamstring issues. Johnson has yet to play in a regular-season game for the Cowboys and has not practiced since straining his hamstring in the first week of camp.
Rookie safety Ahmad Dixon, who impressed coaches during the preseason opener before suffering a concussion, has been cleared to return to practice.