WR Dedric Ward, who was acquired earlier this month, broke his foot on Tuesday during workouts.
Ward will have a screw inserted into his right foot to stabilize the fifth metatarsal bone. Ward is estimated to be out four to six weeks.
Players are scheduled to report to training camp July 30.
"Of course it's disappointing," Ward said. "You never want to start out getting injured, but I'm going to be aggressive with it and be back by the start of training camp. I'm going to do everything to get myself ready."
Ward was signed June 11 to a one-year contract worth $660,000. Because he signed after the Cowboys' final minicamp and on-field activity days, Ward was working on his conditioning.
He had a similar surgery in 2001 on his left foot when he was with the Miami Dolphins. In that case he missed all five preseason games and the season opener.
The Cowboys were looking at Ward as an insurance policy and potential return man because they have little experience behind Keyshawn Johnson, Terry Glenn and Antonio Bryant.