Rob Gronkowski undergoes back surgery; timetable for return unknown

In 11 games last season, Gronkowski had 55 catches for 790 yards and 11 touchdowns. He missed five regular-season games with forearm and hip injuries and the

In 11 games last season, Gronkowski had 55 catches for 790 yards and 11 touchdowns. He missed five regular-season games with forearm and hip injuries and the AFC championship game, a 28-13 loss to the Baltimore Ravens, after he re-broke his forearm.