On the first full day of Steve Kerr's medical leave of absence, the Warriors' head coach came to the team's downtown Oakland facility Friday for treatment on his surgically repaired back and then couldn't help but pop into practice for a little bit.While the players and staff were elated to see Kerr just a day later, player development consultant Steve Nash urged Kerr to go home and rest.Nash played 19 seasons in the NBA, battling a congenital condition called spondylolisthesis - a displacement of the vertebrae in his back.