"It felt good, first one of my career," he said. "I'm just glad my teammates gave me the opportunity to do it."
Even the return to the lineup of star point guard Rajon Rondo couldn't help the Celtics. Rondo, who missed Saturday's loss at Golden State with a bruised right thigh and hip, missed his first five shots and finished with two points and 10 assists.
Pierce scored 20 points to give him 23,189 in his career, passing Adrian Dantley for 23rd place all-time. Jason Terry also had 20 for Boston.
"Winning is hard. I don't know if all our guys get that," coach Doc Rivers said. "You have to play hard to win an NBA game. One game. It's difficult and we're not doing it."
The Kings took a six-point lead midway through the third quarter when Thornton was fouled by Terry on a 3-pointer. Thornton sprained his left ankle on the play when he landed on Terry's foot and left the game.
"When it happened I thought it was worse because it felt so bad at that point in time," Thornton said. "I'm just happy it was a sprain."
Johnson made the free throw to complete the four-point play and make it 63-57.
A 3-pointer by Thomas extended Sacramento's lead to 13 points in the final minute of the third. The Celtics trailed 84-73 after three — the 11th straight quarter they had trailed after on this road trip.
The Kings got off to a fast start with the Celtics playing the back end of a back-to-back and led by 10 early. The Celtics trailed 54-49 at halftime after Garnett beat the buzzer with a layup when the Kings got caught celebrating Cousins' basket with 1.5 seconds remaining.
NOTES: Sacramento's previous triple-double was by Beno Udrih at Cleveland on March 28, 2010. ... Evans will get a second opinion this week on his sore left knee that sidelined him for the 12th time this season. ... Celtics G Leandro Barbosa rejoined the team after going home to his native Brazil to deal with family issues. He entered late and scored two points in 4 minutes.