Dallas swept its two-game trip after an 0-5-2 slump and got its first shutout of the season largely thanks to Lehtonen, who gloved Jarret Stoll's shot from point blank and held it just outside of the goal line late in the second period to preserve the two-goal lead.
"It's one of those things that maybe one out of 50 times you're able to get it," said Lehtonen, who made 27 saves for his 28th career shutout. "It sure felt good and was happy about it, but there's not much to do with goaltending when you're just scrambling and he ends up hitting the glove. But I have to be happy about it."
The Kings saw their four-game point streak end, but more pressing was that their already-thin six-man defensive unit lost another body when Alec Martinez left the game in the second period.
"Once the doctor gives us some more information then that's about all I can tell you," Kings coach Darryl Sutter said.
Dallas, which beat the Arizona Coyotes 4-3 on Tuesday, caught Los Angeles on the second night of a back-to-back - a high-energy 6-5 shootout loss to the Anaheim Ducks on Wednesday -- and kept the Kings at bay in the third period after Lehtonen's glove save paved the way.
"It's a special save," Spezza said. "It shows his athleticism. At the time of the game, the way the flow of the game was going, that was a big save to maintain the lead for us and keep in the game up and be able to continue to be able to play along the way we were playing."
Spezza finished a good-looking sequence when he took Jamie Benn's pass off his foot, moved to the middle of the ice and shot the puck under past defenseman Matt Greene and under Jones at 8:13 of the second period.
Garbutt scored at 13:13 of the first when he wristed a shot on a goal and chipped in the rebound off Jones to complete a big swing after Lehtonen stopped Dwight King on a partial breakaway at the other end.
The Stars took pride in finishing out a win against the defending Stanley Cup champions, especially because they had been 2-1-2 when leading after two periods.
"That's been tough for us and we're still learning what to do and how to play with the lead," Lehtonen said. "We've had plenty leads, but I think tonight we played the way you really need to play when you're up a couple goals. We were putting pucks deep and just playing really solid defensively. All their shots were from the outside. That was nice for me."
It was the Kings' second regulation home loss (7-2-1) and first since their season opener. Goalie Martin Jones gave Jonathan Quick the night off after Quick made 44 saves Wednesday, and he took his second straight loss.
Sutter typically denied that Wednesday carried over into the game, but right wing Justin Williams acknowledged it was a difficult task.
"We chased the game," Williams said. "We chased it from the first period on. In a back-to-back, that's tough. It simply wasn't good enough."
While the Kings are dealing with health issues on defense, young wingers Tyler Toffoli and Tanner Pearson have finally hit a valley. They were benched in the third period Wednesday for ineffectiveness. Pearson has not scored since Oct. 26.
"We need a little bit more from the top end , always," Sutter said. "When you're banged up in the back, you're going to look for chances from your top end players, or what they give you in the tough areas of the ice."
Sutter usually has no qualms about giving defenseman Drew Doughty big minutes but said the extra ice time is becoming a concern. Doughty played 31:39, his fifth straight game of at least 29:46.
"He has been playing a lot of minutes," Sutter said. "Do we like that? No. But that's where we're at. I look at that all the time too. It's too many minutes. He's going to tell you he's fine. But over the long haul, that's too many."
Dallas right wing Patrick Eaves left the game with a lower-body injury and did not return. Right wing Ales Hemsky was a healthy scratch and center Cody Eakin returned after a three-game absence from an upper-body injury. Newly acquired left wing Travis Moen has not yet joined the Stars, who got him from the Montreal Canadiens on Tuesday in exchange for defenseman Sergei Gonchar.