BOSTON — The Celtics seem to be having trouble against the younger, more athletic teams, but they won’t concede that.

They attribute their early-season struggles against athletic teams to playing sloppy on defense and not matching the other teams’ intensity. Because the Celtics are one of the favorites to win the NBA title this year, they get the best out of every team they play and they can’t take any nights off.

Boston coach Doc Rivers said that they were lucky to survive Minnesota and New Jersey’s best games, but they did not match the intensity of the athletic Phoenix Suns, Atlanta Hawks, and Indiana Pacers and lost.

He said that the Celtics have yet to put together a complete game. They hope to accomplish that Friday night, when they host the defending Eastern Conference champion Orlando Magic. The Celtics are 0-2 on Fridays in November.

“It’ll be nice to play them,” Rivers said. “They’re the team everyone is chasing in the East. They won the championship; they’re the favorite. Cleveland is the second favorite and we’re the third, going by the results of last year. It’ll be good to see where we are at.”

“It’s a big game for us,” Boston captain Paul Pierce said. “We’re trying to make a statement against one of the better teams in the Eastern Conference. A team that’s going to be there at the end with one of the best records in the league. If we’re playing for home-court advantage, this is a team we have to beat.”

The Celtics hope to play better defense Friday night than they have in their previous three games. The Celtics have allowed their last three opponents to score at least 95 points.

“We hold ourselves to a higher standard because we feel we’re a pretty good defensive team, but the communication — we just have to pick up and get better at talking on defense and just kind of having that chemistry again,” Boston guard Ray Allen said.

Garnett’s education

Kevin Garnett said he was not scared when he sprained his right knee last season. He explained everything he went through on WEEI on Thursday afternoon.

“I fear God and I fear my mother, that’s about the only thing in life, other than that it was just straight up pain,” Garnett said. “At one point I thought it was something that I could play through; I knew when I got home and when I was in my own personal space, that’s when I knew it was something serious. Walking up steps, sitting down, stretched out on the floor, my leg was constantly bothering me.

“And you’re talking about a lot of activity, so when I really started to take it serious, and the more I got educated on what was going on, that’s when I started to make decisions health-wise, what was best for me. I was running like I was running with a peg leg, and Doc in practice was, like, this is terrible to watch. I was trying to grind through it.

“But I just knew at the same time I was probably making it worse by playing. It wasn’t until I got to see it then I took it a lot more serious, but until that point I was built off hard, but at some point, the mind has to listen to the body.

“So I just sort of zoned out, did all they did for treatment with all these different kind of people. I learned a lot not only about my injury but about my body and how it works and vitamins, and I just got more educated on this whole thing.

Garnett is averaging 13.5 points and 7.3 rebounds per game this year.

roblee@projo.com