Rivers did, however, have an idea how the 37-year-old could help his team.
"Well, hopefully make some shots when we are up 20 in the fourth quarter. That would be nice," quipped Rivers.
Turning more serious, Rivers added, "Paul will be great. Paul, I don't want to overuse him. I know that. So, I don't even know how we are going to use him yet. I want to play him at [power forward] a lot. What I want him to be is healthy in the playoffs. So however we can figure that out, that's what I'm going to try to do."
While Rivers doesn't know exactly how he'll utilize Pierce this season, he does likes the versatility and veteran leadership Pierce adds to a legitimate championship contender.
"I don't know how we're gonna do it with Paul," said Rivers. "Like, I don't even know if I'm gonna start him. It's gonna be interesting. I think it's gonna be great. I just don't know yet. We have a lot of [good] players, which is great."
Also intriguing is the fact Rivers suggested that Pierce's choice of playing locations this season might have come down to Boston or Los Angeles. One year after the Washington Wizards won a tug-of-war for his services, Rivers reveled in getting Pierce to sign a three-year, $10 million contract with the Clippers this offseason.
"I'm really looking forward to him. You know, I think he wanted to go one of two places: One, he'd come back [to Boston], or he wanted to finish his career at home where he grew up," Rivers said while standing courtside at TD Garden as part of a fundraising event for ABCD Hoops Dreams that also featured current Celtics coach Brad Stevens.
"I think it's really cool for me that I get to be a part of [Pierce's Los Angeles homecoming]."
Pierce helped Boston win the NBA title in 2008 and was named MVP of the Finals when Rivers was coaching the Celtics.
Rivers admitted he was disappointed when Pierce chose Washington instead of Los Angeles last summer.
"I wanted to smack him over that one," joked Rivers. "Of course we didn't have any money to give him. Washington had the midlevel; we offered the minimum. And I thought the minimum was a better deal, but he didn't. No, he did the right thing."