Rookie cornerback D.J. Hayden will be out until at least training camp with an abdominal injury, Raiders head coach Dennis Allen said Tuesday. Hayden, the team's first-round pick last month, was admitted to the hospital late last week and will miss the rest of the Raiders' offseason workouts. Hayden had a procedure done to clean out some scar tissue in his abdominal region, the Raiders later announced. There is no timetable for his release from the hospital. Earlier, Allen said it's too early to say if the abdominal issue is related to Hayden's heart injury from last year. "We can't rule that out," Allen said. "Right now, I don't know the correlation to it, but we don't anticipate it being an issue." In November, Hayden severed his inferior vena cava when he collided with a teammate during practice at the University of Houston. It's an injury that typically happens in high-speed automobile accidents, and it is fatal 95 percent of the time. There was a lot of blood in Hayden's abdomen after the collision, so doctors cut through his sternum to find the torn heart vein. A few NFL teams were unsure of Hayden's future after life-saving surgery, but Raiders general manager Reggie McKenzie said medical history was "a non-issue" after he selected Hayden with the 12th pick. Allen, who talked to reporters after Tuesday's workout, said the issue arose Tuesday or Wednesday of last week. He wouldn't discuss Hayden's symptoms. Last Wednesday, Hayden tweeted, "My stomach hurt so bad right now." And though Allen said Hayden should be back by training camp, the time missed is a concern for a cornerback the Raiders were hoping would be starting Week 1. "It's obviously not a good thing from a football standpoint," Allen said. "As a rookie, you need all the reps you can get, and all the work you can get." Cornerback Tracy Porter, meanwhile, is still out with a calf injury. He, Hayden and Mike Jenkins were set to compete for the starting cornerback jobs, along with returnee Phillip Adams.