Heck, if assistant coach Armond Hill didn't set a midcourt screen after Rivers picked up a technical foul for barking at an official in the second quarter, Rivers might have spent the rest of the night watching from the back.
But deep down inside, Rivers actually loved how things were playing out. Knowing his team's veteran legs, playing the second night of a back-to-back after a war with the rival Los Angeles Lakers on Sunday, were not going to be able to run up and down the court with the spry denizens of Lob City, he was secretly content to watch his team get sucked into what Boston's Kevin Garnett would later dub a "bar-style fight."
"If this was going to be a track meet, we had no chance," Rivers admitted. "So we had to muck the game up and I thought we did a good job of that."
Boston seemed caught off guard by the Clippers' attempts to get physical in the early going. The Celtics trailed by double digits in the first half before a couple of second-half rallies helped them to a gritty 94-85 triumph at the Staples Center.
"They came out and played out of their character a little bit -- tough and rough and whatever," Garnett said. "We watched film a lot on these guys and that was totally uncharacteristic of how they play. They're not known for a bar-style fight. They are more finesse -- dunks and all that.
"We knew what it was; we've been in these type of games countless times. We kept our composure for the most part, and then, in the second half, we turned the energy up and got stops when we needed to."
Maybe it was simply a bit of brash postgame chatter toward a young team that was looking for a statement win against the old guard, but the Celtics puffed out their chests a bit after Monday's win.
"Once we settled into the game, we were more physical and pushed back," said captain Paul Pierce, who overcame early foul trouble to chip in a game-high 25 points on 7-of-16 shooting plus seven assists and three rebounds in 31:22 of playing time. "We got up in them, got in their space, made it uncomfortable for them. I think this is a team that likes to be left alone. They play with a lot of finesse, a high-flying team that gets out in transition a lot, all that type of stuff."
Yes, the Celtics knew they weren't going to win a dunk contest, so they turned it into a tractor pull. The Clippers shot just 30.2 percent in the second half and Boston came up with the big stops when they were needed, a stark contrast to Sunday's loss to the Lakers in which the Celtics fumbled away a five-point lead over the final 2:41.
This time around, Boston led by five with 2:47 to go and put its foot down, showing glimpses of a team that has taken great pleasure in winning ugly during the Big Three era.
"Actually, when I was on the bench in foul trouble [in the first half], I was like, 'Man, this is an ugly game,' with the technicals and all the fouls," Pierce said. "But this is our type of game."
Celtics rookie center Greg Stiemsma helped trigger the chippiness when he and Clippers star Blake Griffin got tagged with a double technical for throwing the ball at each other after a first-quarter whistle. Stiemsma once got the better of Griffin in the NBA's summer league, and you couldn't help but wonder if there were lingering issues between the two.
"Maybe for him," shrugged the always-smiling Stiemsma, whom Rivers laughingly dubbed "Mean Stiemsma" after providing 21 physical minutes (though Rivers joked he has to work on his trash talking).
"I didn't have any hard feelings coming in," Stiemsma said. "It kind of started right when I got in. Whatever it was, I can leave things on the floor. Whatever it is, I'm not worried about it. I'm just happy we won."
But if he's learned anything from going up against Garnett & Co. in practice, it's that you have to play with a mean streak to fit in with the Celtics.
"You've got to have flashes of it," Stiemsma said. "You can't play mad all the time. But I'm not going to back down from anybody, either. I don't care what position or situation I'm in. So if I can come in and play physical and take a shot to the mouth or a couple of shots to the head, if it helps us win, I'll do it."
Of course, not everyone thought it was a chippy game. Celtics point guard Rajon Rondo took a little swipe at the Clippers and their on-court bravado after the game.
"It wasn't really physical," Rondo said. "The flopping surprised me. They seemed pretty tough, but there was a lot of flopping out there tonight. That was shocking. I couldn't believe the refs kept going for it, but that's part of it."
The Celtics were more than happy to muck things up. They were even happier to emerge with a win. With former Detroit Pistons bad boy John Salley sitting near their bench, maybe this team found a bit of an identity moving forward.
The Celtics are undersized, with uncertain futures for Chris Wilcox and Jermaine O'Neal, but they showed in the past two games that they're still willing to go toe-to-toe with anybody, including two sizable foes in Los Angeles.
And, as the Clippers learned the hard way, you don't want to push these old-timers, because they've been in plenty of bar fights before and they've won most of them.