WALTHAM — The Celtics  conducted an open practice session for one of their sponsors Monday, which allowed the media a window into their mostly closed off world. NBA teams have been conducting practices in private for several years now, usually allowing the last 20-30 minutes to be open for viewing for the press.
That tends to mean a whole lot of watching guys take free throws, but with the open session we were able to see how hard they work on defense, and how loud and vocal the practices tend to be. The Celtics  worked a lot on halfcourt situations and it had the same intensity as a regular game.
Paul Pierce (bruised left knee) sat out the session. Doc Rivers  said that he shouldn’t have let Pierce play on Saturday against Indiana, but that he let Pierce talk him into it. Pierce tried to sneak on to the court Monday, but Rivers shut him down.
“He’s not going to practice today or tomorrow,”Rivers said. “I told him that after the game. He tried to get on the floor at the beginning, I told him no. he doesn’t miss practices. The only way you can get him to miss is to force him.”
Tony Allen  did take part in his first practice since training camp, but he’s unlikely to see game action, unless as Rivers said, “We need him.”
After the session there was ample talk about what’s been going wrong the last two games, and it starts with the pick and roll defense.
“Our pick and roll coverage is the main thread,” Rivers said. “It’s been inconsistent. It’s two guys not just the guy on the ball. It’s the guy guarding the ball who sets the pick. And then dribble penetration. Some of our defensive sets have been very good and then with five seconds left on the clock the guy dribbling the ball gets all the way to the basket and that’s not just the guy guarding the ball.”
Rivers also said that he thought fatigue was a factor. He blamed himself for working his team too hard during practice last Thursday before a set of back-to-back games. “I made a mistake on Thursday,” Rivers said. “We went way too hard in practice. I thought it carried over to our back to back on Thursday and Friday. I thought we could get away with it, and I was wrong.”
RONDO AT THE LINE: Through 11 games, Rajon Rondo  is sporting an unsightly free throw percentage of 25 percent (3-for-12).
Rivers thinks part of the problem has to do with his Rondo’s revamped mechanics. He equated it to a golfer who tries out a new swing and then goes back and forth between the new and the old.
Kevin Garnett put it in visualization terms. “Practice,” Garnett said. “When you’re in the gym, practice. When you’re eating cereal, practice. When you’re watching TV, practice. When you’re talking to your significant or your mom, practice. It’s all about how you see it. My recommendation for him is just see it. See it go in.”
Rondo asked Ray Allen  about his approach and Allen told him pretty much the same thing. “Rondo has not yet understood or developed a pattern for himself, that’s all,” Allen said. “I think he can shoot free throws. He asked me the other day what do I think about and I told him just my routine. I think about my preparation. When I’m thinking free throws in practice I think about the same thing every time.”
NEW LOOK FOR WEIRD WARRIORS : Golden State is one of the oddest teams in the league. With injuries wrecking their frontcourt depth, Don Nelson  had been playing a lineup that featured Monta Ellis , Steph Curry , Anthony Morrow , Corey Maggette  and Stephen Jackson . That’s essentially three small guards and two swing men.
You can forget about that look on Wednesday when the Warriors come to Boston because they traded the disgruntled Jackson, who has always been a pain for the Celtics, to Charlotte  along with Acie Law  for Raja Bell  and Vladimir Radmanovic .
“That’s a great trade for Charlotte,” Rivers said. “That’s a great pickup for them. It gives them a bona-fide scorer, a go-to guy and a tough guy.”
While it’s true that the Bobcats got the best player in the deal, Jackson also hurts their cap space in the long term. Golden State? The Warriors just got even stranger with Radmanovic, a certified oddball, but a terrific shooter.
BIG BABY UPDATE: The good news on Glen Davis  is that Big Baby is getting smaller. He’s been working out every day since he injured his hand in a fight with one of his friends before the season-opener, and sometimes twice a day.
“He hasn’t gained a pound,” Rivers said. “So that’s a great update. That’s a goal for us is for him to come back lighter. He’s looked good. Some days he comes in the morning and works out and comes back at night and runs more.”
While he can’t shoot with his right hand in a cast, Davis has been working on his off-hand, as well.