WALTHAM — The Celtics were talking NBA championship on Friday. But coach Doc Rivers cautioned that the title road goes through Miami.

It was an optimistic opening day to training camp, and there was almost no holding back regarding the Celtics’ goal. Their offseason deals were not as high profile as the Lakers’ acquisition of Dwight Howard and Steve Nash, plus the offloading of Andrew Bynum to Philadelphia. But the addition of veterans Jason Collins, Courtney Lee, and Jason Terry confirmed the Celtics’ intentions to make a title run.

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“The Lakers are better, getting Dwight, I guess,” Rivers said during media day, marking the opening of camp. “Bynum’s pretty good, last time I checked. So, they’re better, getting Nash. But I could care less about the West. At the end of the day we have to get out of the East, and the defending champions are in the East.

“So, we have Miami. Whatever happens out West, good luck, hope to see you, that’s how we think about it. Miami’s improved, as well. Getting Ray [Allen] made them a better team. Our division is tough. For us, Philly took us to seven games last year, and they add Bynum — size and a go-to guy. Brooklyn is better, the Knicks are better because they will have a whole season under one system. So, it’s going to be harder for us and everyone else.”

The Celtics overcame health problems to reach the Eastern Conference finals last season, losing Avery Bradley (shoulder surgeries), plus Jeff Green and Chris Wilcox, who underwent heart surgeries but appear to have returned at near full strength.

President of basketball operations Danny Ainge emphasized improved depth in the offseason, especially at center and forward. The backcourt lost Allen and will not have Bradley until at least December, but Lee and Terry are expected to compensate.

“I like our team on paper, and now we have to turn it into a team,” Rivers said. “When Avery comes back I think we’ll have the best guard corps we’ve had, at least as far as being deep. I like the fact we have Jason Terry coming off the bench.”

The Celtics will open the exhibition season against Fenerbahce Ulker in Istanbul next Friday.

“A lot of people last year thought that would be our last run,” captain Paul Pierce said. “Making the moves that we did — once I saw we signed the 35-year-old Jason Terry, I thought we’re trying to win another championship. That just shows we’re committed to excellence and we’re trying to win a championship. I’m very excited.

“Danny’s done a really good job of adding depth to this team. We felt like we could have won the NBA championship, but a lot of that had to do with injuries. The added depth will help us going through the season, especially with veterans like myself. These are guys who can really play and can help us out through tough stretches in the season. I think they did a tremendous job of adding to our team.”

Pierce also received an unpleasant surprise when Allen signed with Miami.

“I was very surprised at Ray’s decision,” Pierce said. “I thought we were going to finish our careers together — me and Ray and Kevin [Garnett]. I was very surprised, him going to Miami. He has to make a decision he feels is best for his family and for himself. I wished he had gone to the Clippers, if anywhere, and not our Eastern Conference rivals.”

Pierce started last season slowly while recovering from a foot injury that limited his training camp participation. Pierce said he contemplated retirement last season, partly because Garnett indicated he might be retiring. The captain hinted he may be ready to walk away when Garnett’s current deal is up.

“Hopefully, I can be around next year and the year after,” Pierce said. “The goal is to hopefully retire with Kevin. He just recently signed a three-year deal, so I see my career kind of ending along the path of his.”

Pierce also said he is healthier than last season at this time.

“Coming into camp this year, I’ll be ready,” Pierce said. “It’s really hard to get into shape coming into camp with an injury, especially basketball shape.

“With the minutes, I’ll leave it all up to Doc — watch how I’m playing, and if I can still play at a high level, who knows what the number will be? Doc has always found a good balance. I’ll listen to my body. At this age, guys’ bodies tend to break down. I take care of myself and, hopefully, I can continue to play at a high level to help this team win a championship.”