For the Celtics, facing the boy they watched grow into a top-10 NBA draft pick during his dad’s nine seasons in Boston, it was weird to finally see Austin Rivers looking back at them on the parquet in a Hornets uniform.

“It’s just a strange dynamic,” said Celtics coach Doc Rivers after losing to his son, 90-78. “I didn’t enjoy it, honestly. I know it’s neat for everyone else, but as a father, I don’t know if I enjoyed that.”

“It was strange for everybody in here,” added Kevin Garnett. “If we didn’t feel old [before], we feel a little old [now], obviously, seeing a little kid that used to say absolutely nothing, dribble his ball and kind of be in his own little world to being a young man now in the league, trying to make something of himself, doing a good job of it, talking trash, running up and down, leading his team. It’s good. It’s good to see Austin doing real good.”

Garnett might have wanted to seem do a little worse, actually, since Austin’s eight points on 3-of-6 field goals — including a running layup during their momentum-stealing run in the second quarter — marked his best scoring and shooting night this month. His 23 minutes were more than he played in his previous three games combined.

Maybe that’s why it was the 20-year-old Rivers who felt the most comfortable in such a strange situation.

“It’s fun to get to compete against your family,” he said. “I’m sure if you have a brother or sister, you always wanted to win. It’s the same thing here. Even though it’s at a higher level, I always want to try and beat him.”

He did beat his father — even joking, “Doc got the L; he can’t beat me” — but would he ever join him? While Austin didn’t rule out playing for his dad one day in Boston, he first wants to find his way in the NBA.

“Not right now, but if the situation ever arises,” said Rivers, who is under New Orleans’ control for $15 million over the next five seasons. “It’s a blessing to play in this league. Whatever happens, just happens. I expect to just keep working hard and become the player that I want to be one day, and that’s going to take a lot of hard work and effort. That’s what I’ve got to keep moving for. If I ever play here, then I play here, but I love where I’m at right now.”

In the meantime, the Celtics and Austin Rivers will just have to admire each other from afar.

“I still want them to do well,” he said, sounding much like his father. “Obviously, when we play them, I’m trying to win, but I watch a lot of their games and I want them to do well, just because I know a lot of those guys.

“Obviously, I want my dad to do well, just because he’s invested so much time and he never sleeps. In the summertime, when I’m home and I’m working out, I go hang out, I come back at night and I go for a snack at 4 in the morning, he’s still up doing stuff with basketball. It’s crazy.

“So, I just want him to always do well, because I love him.”

Garnett reciprocated. “We root for him, obviously, when he’s away from here,” said KG, “but tonight was a little odd. I’ll admit it. It was a little odd. He’s family, but we all hit the floor, we’re all trying to win. But it was odd.”