By Matthew Geagan, CBS Boston

BOSTON (CBS) — Celtics head coach Brad Stevens tried his best to slow down the Payton Pritchard Hype Train ahead of Tuesday night’s game against the Pacers. But as the game went on, it looked like Stevens was the conductor of that very train.

Really, it’s been Pritchard himself steering the locomotive with some outstanding play on the floor. The 22-year-old rookie doesn’t look anything like a 22-year-old rookie, and his coach certainly isn’t treating him like on.

Pritchard played 27 minutes off the bench in Tuesday night’s win over the Pacers, playing the role of sparkplug in a 17-point comeback victory by Boston. He logged some key crunch time minutes in the fourth quarter, including a stint with the starters to close out the game. He turned in 10 points off 4-for-8 shooting to go with five assist and five rebounds, not to mention a handful of hustle plays on defense.

Fans are buying the Pritchard hype — and so are his teammates.

“Payton is the GOAT, man,” Jaylen Brown said after the victory.

JB sounds like a Celtics fan with that proclamation, but he’s had a front-row seat for the FastPP Show over the last week. And Pritchard’s impact goes far beyond his impressive stat line.

Pritchard provided a much-needed jolt of energy when he was on the floor, a jolt that the Celtics carried throughout the final 15 minutes of the game. It didn’t matter if he played with reserves or alongside starters; Pritchard made an impact. He was even handed the keys to the offense in the fourth despite the fact that veteran Jeff Teague also on the floor.

Basically, Pritchard was everywhere and doing a little bit of everything when he was out there. It gave Stevens boatloads of confidence in keeping the rookie out there in any situation.

“We had him running all kinds of pick-and-rolls in the second quarter and the start of the fourth,” said Stevens. “He’s poised off that stuff, he makes the right play. He’s deceptive so he can get in, use his body and finish as we saw on a couple of occasions. He’s a guy who knows how to play.”

“Payton came in there with the confidence,” added Brown. “Definitely needed a spark coming off the bench and Payton was everything and more for us tonight. We’re gonna need more guys to continue to step up. Excellent guy. Excellent job from Payton Pritchard, man. Kid can play and we’re looking forward to him and other guys stepping up as well in the future.”

Pritchard had a couple of nice driving layups during Boston’s epic run to erase a 17-point Indy advantage in the second half. And even when things didn’t go his way, he found a way to make sure they did.

With Boston up by four points with five minutes remaining, Pritchard threw a bad log to Tristan Thompson down low that Oladipo was able to grab. Oladipo raced down the floor, but Pritchard booked it after him, chasing the Indy guard down from behind.

Pritchard was able to poke the ball away, and on the other end, he made a great transition feed to Marcus Smart for an open three, giving Boston a seven-point cushion with 4:46 to go. Indiana was worried that Pritchard would drive to the hoop, resulting on three Pacers keying in on him. It left Smart wide open for his three.

Those are the kinds of plays that have Stevens feeling so confident about sending the rookie out during important stretches. And that confidence from his coach have Pritchard feeling like he could do anything.

“Having that confidence from your coach and also from my teammates, it means the world to me because it can allow me to keep growing as a player and being able to help this team when I can,” said Pritchard. “Coming off the bench, I want to be able to provide a spark, either get the team going or help the team build more of a lead.

“I’m all about winning. This is why we play this game,” he added. “I want to win and I want to help as much as I can to get a win.”

Boston drafting Pritchard at No. 26 in November was initially met with some criticism. While the Celtics needed more guard depth with Kemba Walker out for the start of the season, another unisized point guard wasn’t seen as the best avenue to address that need. But through four games, Pritchard is showing why Ainge used that first-round pick on a four-year college kid.

Pritchard knows how to play the game and it’s made his transition from college to pros rather seamless. He’s logged 88 minutes of action over his first four NBA games, which ranks fifth on the Celtics — ahead of guys like Teague, Daniel Theis and Grant Williams. He’s producing when on the floor, but more importantly, he’s giving the Celtics some much-needed energy off the bench.

It’s a small sample size, but so far, Pritchard looks like he could be the steal of the 2020 NBA Draft. More importantly, he looks like he’ll be a valuable contributor to the Celtics throughout the season.