What is Rondo's magic number?

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Celtics coach Doc Rivers is trying to reel in Rajon Rondo's minutes moving forward.WALTHAM, Mass. -- Boston Celtics coach Doc Rivers acknowledged Monday that he has to do a better job of keeping Rajon Rondo's minutes down, if only to maximize his point guard's efficiency when he's on the floor.

Rondo is averaging a whopping 41.7 minutes per game through three contests, nearly five minutes more than his regular-season average from last season (and more than nine minutes over his career average). His stat line is hard to ignore with the extra floor time, averaging what would be career-highs at 15.3 points, 12 assists, and 5.3 rebounds per game.

Rivers doesn't worry about Rondo's minutes the way he does with 35-year-old Paul Pierce or 36-year-old Kevin Garnett, but admitted that minutes number has to come down moving forward. The Celtics have leaned hard on Rondo early in the season while posting a 1-2 mark.

"I’m concerned, not as far as him getting tired, but I don’t want him to save himself on the floor," said Rivers. "There’s a minutes number for him, we don’t know what it is for him yet -- we’ll figure it out -- where he can play his minutes at full pace, instead of knowing he’s going to be on the floor too long and then he starts pacing himself. We need him to be a fast, quick, aggressive player."

Rondo is no stranger to heavy minutes, averaging 42.6 per game in the playoffs last season (and 38.5 per postgame game for his career). At age 26, and being the team's only true point guard, Rondo expected a heavy workload this season, but Rivers wants to keep him operating at full throttle, particularly on the defensive end where a high energy level is necessary to maintain the brand of defense Boston desires to play.

"I think [his minutes number] in the 39s [or] 38s," said Rivers. "Not much lower than 40, but it’s in that area."

For what it's worth, the Celtics are 49-39 when Rondo, now in his seventh season, plays 40+ minutes during the regular season. Even without a pure backup ball-handler, expect Rondo's minutes to come down, particularly if the Celtics start getting more from their bench, defraying the load the veteran core of Rondo, Garnett, and Pierce are carrying at the moment.