WALTHAM — During Tuesday’s practice, backup point guard Keyon Dooling  pulled Celtics  coach Doc Rivers  aside to talk about the second unit’s identity. Among the things Dooling noticed was that the reserves were trying too hard to emulate the first team’s offensive approach, a difficult task considering the relative talents of each unit. Rivers agreed.
The conversation illustrated Dooling’s assertive attitude and keen insight, both of which have impressed Rivers throughout training camp. “I knew [Dooling] is an energy player,” Rivers said. “But energy players don’t usually mean high IQ [players. Where Keyon has surprised me is he really thinks the game.”
Rivers said Dooling has made for a seamless transition to his new team and that he understands the offense as well as some of the players who have been here for years. His high basketball acumen gives Rivers the luxury of versatility. In Sunday’s preseason game in Toronto, the coach experimented playing Dooling at shooting guard, despite not having practiced at the position.
Dooling is confident he can make the transition between guard spots when necessary. “Right now everything is on the fly,” he said. “I learn fast. I know the [shooting guard] position and where to be even though I haven’t gotten the reps [in practice]. Wherever the opportunity presents itself, I’ll be ready.”
The well-traveled guard is an integral part of the Celtics new-look rotation and Rivers is looking for major improvement from his bench players this season.
“Last year we failed miserably,” Rivers said. “Me [included]. We didn’t do the bench [well] and the bench didn’t save us ever. It lost some games for us, but it didn’t save us in a lot. This bench, the one thing I do like, they’re not going to back up. That doesn’t mean they’re going to play well, but I like they’re a tough group. They respect the starters but that’s about it. That’s all they’re getting.”
Rivers loves the fact that Dooling will challenge Rajon Rondo  every day in practice.
“Rondo has laughed about it several times, this guy doesn’t back up at all and it’s been great,” Rivers said. “They go at each other in a positive way. I think it’s the first time Rondo’s had that and it’s been great for him.”
Dooling hasn’t appeared in the playoffs since 2008 with the Magic and he feels rejuvenated about playing for a team with high expectations. “This is my best opportunity to compete for a [championship],” he said. “I’m very aware of that. I’ve been out of the playoffs the last few seasons, so my window has suddenly opened up.”
If the Celtics window is going to stay open they’ll need strong performances from players like Dooling.