ATLANTA -- Michael Garnett did exactly what the Atlanta Thrashers needed him to do.
But it was the other side of the ice where the difference was made.
"Defense was the main part of the game," said Garnett, the Thrashers' rookie goaltender. "There were not too many chances either way."
The Thrashers won their third straight and fourth in five games.
"When you look at teams that are being successful, it starts with your goaltending," Atlanta coach Bob Hartley said. "I think he is developing some good confidence. That's contagious."
Florida goalie Roberto Luongo stopped the first 24 shots he faced, but he lost a 1-0 lead with 14:36 remaining when Slater put a wrist shot between his legs.
"We played a good 60 minutes," Luongo said. "Unfortunately, they got a lucky goal and then they bounced right back and got another."
Kovalchuk scored his 21st goal by knocking in his own rebound just outside the bottom of the left circle.
Garnett made 27 saves for Atlanta, improving to 7-7-2.
"They have scored a lot of goals for me to win some high-scoring games," Garnett said. "So I feel obligated now to keep them in the games and give them the opportunity to win some low-scoring games."
The Panthers, who have won just three of 22 road games, extended their franchise-worst streak. Their last road victory was Oct. 25, a 4-3 overtime victory over Pittsburgh. Florida remained tied with St. Louis with an NHL-low two road victories.
Nathan Horton's 15th goal, a wrist shot from the bottom of the left circle, gave the Panthers a 1-0 lead at 15:36 of the second period.
Since returning from a knee injury on Dec. 1, Horton has eight goals and an assist in nine games. Horton entered with an NHL-best 26.4 goal percentage on 53 shots.
Kovalchuk has recorded a point in 16 of 21 games, scoring 16 goals in that span.
Luongo made 29 saves, including one on Marian Hossa's penalty shot 1:04 into the game. Hossa was on a breakaway when Mike Van Ryn pulled him down.
"I didn't see either goal because I separated my right shoulder," said Van Ryn, who returned later in the third. "It was a one-goal game. It was hard-fought on both sides. Unfortunately, we had those breakdowns."
Marc Savard, who scored the game-winner with five seconds remaining in overtime Thursday night at New Jersey, had his 31st assist on Kovalchuk's goal.
Olli Jokinen had his 18th assist for the Panthers.
Atlanta captain Scott Mellanby, a 20-year veteran, likes how Garnett has played as the Thrashers wait on Kari Lehtonen and Mike Dunham to return from injuries.
"He has handled the situation really well," Mellanby said. "You have to have at least 92 points to make the playoffs. That's 10 games above .500. Right now we are two games below. We need to be 12 games over the rest of the way."
Atlanta, which entered with the NHL's fifth-best power-play unit, went 0-for-3. ... Luongo has stopped all eight penalty shots he has faced, including four this season. The others were against Carolina's Erik Cole, Philadelphia's Peter Forsberg and Miroslav Satan of the New York Islanders. ... Florida C Joe Nieuwendyk played 20 shifts after missing two games with back problems.