Coming into training camp, the hierarchy of the Celtics' roster appeared to fall into place naturally for coach Doc Rivers. Kevin Garnett, Brandon Bass, Paul Pierce and Rajon Rondo would start, with Courtney Lee filling in at shooting guard until Avery Bradley's surgically repaired shoulders healed. Jason Terry and Jeff Green would be the first players off the bench, with Chris Wilcox, Jared Sullinger and Darko Milicic close behind. Just one week into camp, though, nothing seems certain for Boston from a lineup standpoint. Suddenly, Terry, Sullinger and Milicic are potential starters, Wilcox has been limited by back spasms and Garnett could be headed back to power forward temporarily. Either Rivers is operating at a different level of consciousness than almost every other coach in the league, he has gone completely bonkers or he just has too much talent on hand to know what to do with. The latter portions of Celtics practices have illustrated the wide-open roster setup. Nine players have spent time running with the first team, including rookie center Fab Melo, who would seem to be a longshot to be one of the final 15 players to break camp. Working in that many different players has been a challenge, Pierce acknowledged, but he likes it that way. "That's why we work on it," Pierce said Thursday at the team's practice facility. "Of course it's tough. It's tough being great. That's why you come in here and you work on it every day. You learn from your mistakes and we continue to build and get better." The "green" unit on Thursday consisted of Pierce, Garnett, Rondo and Terry, with Melo and Sullinger subbing in. Green has run with the "white" squad almost exclusively this preseason, although he is the most likely candidate to join Garnett, Pierce and Rondo on the floor at the ends of games. Bass and Lee, meanwhile, have not been ruled out of the conversation of potential starters, and Bradley is lurking on the sideline, itching to play. It is tempting to tinker, and Rivers has not been able to resist experimentation. On Wednesday, he disclosed that he has considered replacing Bass in the starting lineup with Sullinger or slipping Garnett over to the four while starting Milicic at center. Terry, the consummate sixth man, might even be on the floor for tip-off regularly for the first time since 2007. Rivers is aware that he could do too much, yet he stressed on Thursday that there would not be nearly as much juggling as one might expect.