Days into preseason camp, the Dallas Cowboys already have reason for concern after quarterback Dak Prescott left practice early Wednesday with a shoulder injury. 

Prescott walked off the field at Cowboys camp in Oxnard, California after experiencing soreness in his right arm. 

The team said later that an MRI exam revealed a muscle strain in his right shoulder and will be "evaluated on a day-to-day basis." 

Wednesday was to be Prescott's first practice with the team in full pads since his 2020 season ended in Week 5 with a fracture-dislocation of his right ankle. 

Prescott, who turns 28 on Thursday, downplayed any concerns in a statement released by the team. 

"I felt some soreness when making certain throws today, and I really just decided not to push things too far," he said. "Better to be cautious and smart about it.

"I don't see this as any kind of serious setback. We'll treat it on a daily basis, and I'll be fine." 

Prescott is entering his sixth season as the Cowboys' quarterback. In 2019, his last full campaign, his career-best 4,902 passing yards were second in the NFL to Jameis Winston (5,109), and his 30 touchdown passes ranked fourth in the league. 

Garrett Gilbert ran the first-team offence in Prescott's absence for the rest of Wednesday's practice. 

The Cowboys have one more preseason game than most teams, the August 5 Hall of Fame Game against the Pittsburgh Steelers in Canton, Ohio, but Prescott was not expected to play in that contest anyway. 

Dallas will open the regular season September 9 away to Tom Brady and the Super Bowl champion Tampa Bay Buccaneers.