The back pain that threatens to keep Golden State Warriors coach Steve Kerr out for the rest of the NBA playoffs is a setback for the team, but colleagues on Thursday said they were more concerned about seeing someone they admire suffer so much. News that the pain and headaches that kept the 51-year-old coach away from the team for the first 43 games last season had returned earlier this month shocked fans in the Bay Area, where Kerr is a beloved figure. It is even more difficult for those inside the organization, who have developed a deep bond with the coach who is as well known for his ability to connect with players as he is for his high basketball IQ.