Paul Pierce is undecided on the invitation to return to the Los Angeles Clippers for his 19th NBA season.Clippers coach Doc Rivers disclosed during a fundraiser at TD Garden in Boston that Pierce was on the fence about playing in 2016-17."Paul has had the summer, he's gone back and forth," Rivers said. "I think he has a right to do that. I really do. Paul didn't have the best year last year. I don't think he wants to go out that way. So I think that's why he's working to try to come back. But he still may change his mind next week. So we just have to wait. I told him if I see him at training camp, I'm assuming he's playing."Pierce spent most of his career in Boston, including winning the NBA championship in 2007, before he was traded to the Brooklyn Nets. He reunited last season with Rivers in his home state, but Pierce did not have a major impact off the bench as expected. Rivers said there is no question Pierce can still be effective if he wants to play."If I don't think they can play, then I tell them that. But I think Paul can play," Rivers said. "I don't know how much he'll play, but he can play. I've always thought it's easy for someone else to tell you to retire; I think that's something that the player has to come to by himself."I just think Paul loves to play."Rivers said he also talked to Ray Allen, who was part of the '07 team in Boston but didn't play in the NBA last season, but Rivers declined to share whether Allen plans to come out of retirement this season."I won't talk about what we talked about. I think if Ray was in the right spot, he may play," said Rivers.