WALTHAM — The Celtics  have long prided themselves on their toughness and while it may have manifested itself in a sneer here or a posedown there (along with lots and lots of on-court talking) when the Celtics talk about real toughness they mean things like playing aggressive help defense, fighting through screens and rebounding.
Take the game on Friday against Indiana. The Celtics lost primarily because they got killed on the boards — the Pacers had 14 offensive rebounds.
“The difference in the game was Indiana was tougher,” Celtics coach Doc Rivers  said. “They made tougher plays, they were more physical. The game was there to be won by either team, it was who was going to grab it.”
Part of this may be related to conditioning. Rivers took some of the blame for not conducting harder practices when he had the chance, so he ran them through a workout on Monday that was heavy on running.
The coach said the practice was “sloppy,” but also productive. He doesn’t feel their conditioning is where it needs to be yet, but it’s better than it was a few weeks ago. In addition to running them into the ground, the Celtics also went back to their core elements.
“We’re focusing on ourselves right now,” Rajon Rondo  said. “We’ve got a lot of things that we have to work on. It’s starts with ourselves. We have to look into the mirror and dig down deep and try to find a way to start being basic and get back to the basics.
In general, Rivers is happy with his team. They have great chemistry and they’re willing workers, but it comes down to that word again: toughness.
“We can get along but I want to win too,” Rivers said. “The chemistry is phenomenal. I couldn’t ask for a better group of guys, but I may be asking for a tougher group of guys. I’m not sure yet.”
This has manifested itself on offense where the Celtics are attempting less than 20 shots per game at the rim, one of the lowest numbers in the league. “We’re a jumpshooting team and then we’re a pick and roll team,” Rivers said. The good news is they’re making those jump shots as well as ever, but on nights when they don’t fall they haven’t developed a reliable post game.
But defensively, and on the glass, the Celtics have slipped noticeably through the first eight games. They rank 20th in points allowed per 100 possessions — they’ve never been lower than fifth since Kevin Garnett  arrived — and 20th in defensive rebounding percentage.
“We watched a long film today and it showed them everything,” Rivers said. “It’s guards getting beat off the dribble, bigs helping, opposite weakside guard not cracking back on box outs. We had five times [against Indiana] where we had the inside position on a rebound, and it was our bigs and they still got the rebound. To me, that’s physicality. It’s not boxing out, it’s relying on your athleticism. Five times they came and scored on every single possession. That’s the game the other night.”
With the caveat that it’s still early in the season, a few trends have emerged. Paul Pierce  has been great on the defensive boards, grabbing more than five a night. His defensive rebounding percentage of 21.1 percent leads all small forwards. Rondo has also been getting his share and is once again one of the top rebounding point guards in the league, although he chalked that up to a few lucky bounces.
“They’re just finding me, I guess,” Rondo said. “I’m finding it a little bit, but the balls are coming to me. If you watch the game a lot of them come right to me and I’ll get in there every once in a while and use my athleticism to try and jump and get those.”
But a lot of this falls on the big men. It went mostly unnoticed because his minutes were down, but Garnett was a monster on the defensive boards last season. He was the biggest reason the Celtics ranked in the top 10 in defensive rebounding. Garnett, Jermaine O’Neal  and Brandon Bass  have had a handful of huge rebounding games, but the consistency isn’t there yet. In limited minutes, Chris Wilcox  has not provided much help on defensive glass.
That’s a big reason, but far from the only reason, why the Celtics are 4-4. If their outside shots aren’t falling, they’re having a hard time finding ways to score and it’s difficult to outscore teams when you’re getting beat on the other end and on the glass.
“We’re big believers in trusting each other and right now we’ve got to keep believing,” Rondo said. “We’re struggling right now at 4-4. We haven’t started out this bad in a long time. The results are about the end of the day and we’re a long way from the finish line.”
Rondo also knows that the Celtics will get no sympathy from the rest of the league while they try to work through their problems.
“We still have the bullseye, even though we’re old guys,” Rondo said. “Teams want to try and take advantage of us. It’s happening a little bit, but we’ll be fine and we’ll get back on track.”