Luka Doncic scored 39 points and the short-handed Mavericks jumped on Golden State from the start to thump the Warriors 133-103 on Tuesday night.
"Biggest game of the year and it was over before it started," said Kerr, whose team trailed by as many as 43.
Stephen Curry scored 27 points with five more 3-pointers, extending his NBA record for 3-pointers in a month to 90 in April. He had passed James Harden's 82 in November 2019 on Sunday.
"Chasing Steph Curry around has got to be the hardest job in all of basketball, pro, college, international, you name it," Dallas coach Rick Carlisle said. "The guy has been on just a tear over the last month. Trey Burke rose to the challenge, he just chased him all over the place and we had plenty of help."
Tim Hardaway Jr. added 13 points and seven rebounds off the bench as the Mavericks got 60 points from their reserves a night after losing 113-106 in Sacramento.
Just when the Warriors were determined to gain some momentum for the important stretch run, they delivered a dud and had their four-game home winning streak snapped.
"It was the perfect storm of everything going wrong tonight," Curry said.
Golden State didn't defend the perimeter, where the Mavericks shot 18 of 35 on 3-pointers.
The Warriors went 9 minutes, 40 seconds without scoring spanning the first and second quarters and were just 5 for 27 midway through the second quarter. That drought eventually led to a 47-16 hole.
"I'm not concerned about the scoring drought, I'm concerned about defense, I'm concerned about a level of intensity and preparation and competitiveness," Kerr said. "That's what was missing. I'm the head coach. I did not have them ready to play, clearly."
Doncic shot 15 for 23 and added eight assists and six rebounds. Dallas has won seven of nine against Golden State and four in a row on the Warriors' home floor.
The Mavericks made nine of their initial 15 shots to go ahead 25-12 and force a Golden State timeout at the 4:58 mark of the first.
"It was the complete opposite from yesterday. It was crazy," Mavericks forward Maxi Kleber said. "They couldn't make any shots. ... I don't even know how to describe it. We just went with the flow."
JJ Redick played seven minutes for the Mavericks after being questionable with soreness in his right heel. Boban Marjanovic was ejected with 2:39 left for a Flagrant 2 foul, raising his arms in the air at the crowd as he disappeared down the tunnel.
Mavericks: C Kristaps Porzingis (sprained left ankle), G Josh Richardson (right hamstring tightness) and G Tyrell Terry (personal reasons) sat out. ... Dallas has won six of the last seven with Golden State and is shooting 45.3% (139 for 307) from 3-point range during that stretch.
Warriors: F Eric Paschall did more 3-on-3 work Tuesday and is scheduled to play 5-on-5 on Wednesday before the flight to Minneapolis. "We're hopeful that he'd be able to play at the end of the road trip - Houston or New Orleans," Kerr said. ... G Gary Payton II has impressed Kerr: "We love Gary. He's an elite defensive player. He's someone who can come into the game and make an impact," Kerr said. His second 10-day contract wraps up Wednesday. ... Golden State also won four in a row at home from Feb. 15-Mar. 14.
The Warriors hosted Samba Guisse as their "Impact Warrior" for his everyday leadership in the community. A security guard for the Department of Public Works at the Civic Center/UN Plaza, Guisse stopped an attack on a 76-year-old Chinese woman last month on San Francisco's bustling Market Street.
He was honored during halftime for his courage and all he does on the job for others.
Guisse, 44 and originally from Senegal, insists it comes naturally and his family taught him these values.
"I just do it in my heart," he said, not expecting any fanfare. "Each person should help everybody, it doesn't matter what race you are, you're white, Black, Asian. I wasn't expecting it was going to be like this. I've been in the job for a long time. I help people all the time."
Mavericks: At Detroit on Thursday night to face the Pistons for the second time in nine days.
Warriors: At Minnesota on Thursday night to begin a four-game road trip.
Luka goes for 39 points in blowout of Warriors
Luka Doncic torches the Warriors for 39 points as the Mavericks cruise past the Warriors.