Austin Reaves dropped 36 points in the Lakers’ lopsided loss to the Celtics on Friday. But very little of that production came against the player who’s emerged as Boston’s new defensive stopper, Jordan Walsh.

Walsh, given the Reaves assignment with Lakers stars Luka Doncic and LeBron James both inactive, defended Los Angeles’ breakout guard on more than 45% of the LA’s possessions and held him to three points on 0-of-3 shooting with one block, according to NBA player tracking.

The rest of the Lakers’ roster also had minimal success against Walsh. Opponents shot 1-for-5 and 0-for-2 from 3-point range against him in Boston’s 126-105 win at TD Garden, totaling five points and three turnovers.

After the game, Reaves gushed about Walsh’s defensive potential.

“He just plays hard as crap every single possession,” he told CLNS Media’s Bobby Manning. “He don’t take a possession off. His abilities, his length, his athleticism. He’s physically gifted, moves really well. I could see him being one of the best defenders in the league for many years to come. … He’s a good player.”

Those defensive abilities, coupled with the experience and confidence he’s built over his two-plus seasons in Boston, have helped Walsh vault from deep reserve to highly impactful starter over the last month. He’s matched up against a parade of All-Stars — Tyrese Maxey, Jaren Jackson Jr., James Harden, Cade Cunningham, Anthony Edwards, Donovan Mitchell, Jalen Brunson, Karl-Anthony Towns and more — and the Celtics are 9-2 in games he’s started.

Walsh isn’t just making an impact on the defensive end, though. He’s also upped his offensive production, scoring at least 14 points in three of his last four games at a hyper-efficient rate.

The 21-year-old, who’d never scored more than 10 points in an NBA game before last weekend, has made 19 of his last 20 field-goal attempts, including 5 of 6 threes during that span.

Against the Cleveland Cavaliers last Saturday, Walsh notched his first career double-double with 14 points and 11 rebounds. Tuesday against the New York Knicks, he outscored teammate Jaylen Brown in the fourth quarter to help Boston secure one of its most impressive home victories of the season. He then tallied a career-best 22 points on 8-of-8 shooting Thursday in a 146-101 battering of the Washington Wizards, followed by a 17-point effort against the Lakers that included a career-high four made 3-pointers.

Walsh’s averages during Boston’s current four-game winning streak: 15.3 points on 84.6% shooting (66.7% from three), 7.0 rebounds, 1.5 assists, 1.5 steals and 1.3 blocks in 28.2 minutes.

“It’s been great,” said Brown, who advocated for Walsh’s recent uptick in playing time. “It’s been great. Honestly, it’s been great. I don’t want to boost his head up too much. I don’t want him to start getting cute. He’s got to still take care of the details, but he’s been doing a good job. But we’re going to need him to maintain that, so y’all don’t boost his head up too much.”

Per Cleaning the Glass, Walsh ranks in the 87th percentile among all NBA wings in steal rate (87th), block rate (96th), defensive rebounding percentage off missed field goals (88th), offensive rebounding percentage off missed field goals (97th), effective field-goal percentage (96th) and points per shot attempt (98th). He’s been an all-around difference-maker — and one of the biggest reasons for Boston’s surge up the Eastern Conference standings.

As of Friday, the 14-9 Celtics, who began the season 0-3, sat just one game back of second place in the East.