It now appears that Hayden's injured right foot -- which he rolled several weeks ago -- might be more serious than originally expected. The injury could keep the second-year defensive back out until training camp.
"It's hard to tell," Allen said Monday, per CSN Bay Area. "Initially I was hopeful (that he would return soon). We're day-by-day with DJ. Hopefully we'll have him out here, because he needs the work."
After being drafted No. 12 overall in 2013, Hayden missed most of last year's offseason program following abdominal surgery. He also missed the final eight games of the 2013 season after suffering a groin injury.