No player under Doc Rivers’ glare has crossed a more challenging proving ground than Jeff Green. But the Celtics forward appears to have reached an important point in the course.

Rivers is finally pleased enough not only with Green, but with the combination of Green and Paul Pierce at small forward and shooting guard to admit the former has earned a regular place in the starting lineup.

“I think he’s earned that,” Rivers said of Green, averaging 23 points in his last six games. “His confidence is high, and when you have that, you think you can do anything. You think you can jump off a building. That and knowledge, being around our system longer. Coaching-wise, we’re switching more than we ever have because we’re comfortable with it as well.

“I wasn’t going to give it to him. Starters have to be more consistent. Bench players are inconsistent guys who have gone up and down. Jeff has earned that, and I’m really happy, because he makes everyone better.”

Though lineups are always subject to matchups, Rivers has finally been won over by a combination he didn’t like early in the season. He didn’t believe Green was adapting well to small forward, with Pierce in the unlikely role of 2-guard.

Indeed, in the interim Green appeared to have his best moments against slower power forwards. But with Kevin Garnett out of the lineup the last seven games and Chris Wilcox inserted at center, the chemistry finally worked.

“Early in the season it was bad,” said Rivers. “We started camp with that lineup and it wasn’t very good. It was more (a problem) in the defensive end, but even in the offensive end when they would both run into the post. It just took time. Jeff needed to get more comfortable. I didn’t want to throw him into the same spot as when he first got here, where we were trying to throw him at the 3 and the 4 at the same time. Now we’re saying 2, 3 and 4. We made a conscious effort to stay away from that lineup until we thought Jeff was right.”

Of equal, if not more, importance is Pierce likes the change, especially when given the opportunity to exploit mismatches against smaller guards.

“The thing is, it’s going to be difficult for most guards to match up with me on most nights, especially in the Eastern Conference,” said Pierce. “You’re not talking about having to guard Kobe (Bryant) or (James) Harden. Other than (Dwyane) Wade and a couple of other guys like Monta Ellis who can really put the ball in the hole, I think it’s a complete nightmare for a 2-guard to have to matchup against me.”