Now that three members of the rotation, including a franchise-level point guard, are out of the lineup for the rest of the season, more is being asked of everyone. In the case of Avery Bradley and Courtney Lee, that call is something most players would have no problem accommodating. Doc Rivers has told his starting backcourt that they need to score more, even take the lead from time to time. As the Celtics coach recently said, it’s not hard to motivate a player offensively. But Bradley defines himself defensively, gets his primary charge from shutting someone down. Though his development as a shooter, driver and cutter is getting there, scoring is his next frontier. Lee is a fine complementary scorer, especially in transition. But in a reconfigured Celtics offense that stresses ball movement and balance, he also has to produce more. That’s the demand both players carried into last night’s game against the Lakers. They both certainly started strong Tuesday night in Denver, each scoring 12 points in the first quarter on 10-for-15 combined shooting. Lee finished with 15 points and Bradley 17, on 13-of-25 combined shooting, in the 97-90 loss to the Nuggets. “We need that for the rest of the season,” said Rivers. “Right before the (all-star) break, I talked to Avery about it and Courtney. We have to be a little more aggressive. We have to use them more in pick and rolls and attacking the basket. They were pretty good.” Kevin Garnett, who seemingly would always rather see a teammate score instead of himself, loves the plan.