Diggs isn't present for mandatory minicamp, Alaina Getzenberg of ESPN.com reports.
Sean McDermott told reporters he's "very concerned" by Diggs' absence, though the Bills head coach didn't provide an explanation for why the star wideout isn't present. This isn't necessarily a contract dispute, considering Diggs signed a four-year extension last spring. The 29-year-old hasn't participated in voluntary team activities this year, though that's not exactly abnormal for a veteran player of his caliber.