WASHINGTON - Tomas Vokoun wasn't seeking revenge or trying to prove anything against his former team. His main motivation was simply to win another game for the Washington Capitals.

And that is precisely what he did.

Vokoun stopped 20 shots in his 45th NHL shutout, and the Capitals beat the Florida Panthers 3-0 on Tuesday night to improve to 5-0, the best start in franchise history.

Marcus Johansson, Alexander Semin and Jason Chimera scored for the Capitals, who led 1-0 heading into the third period.

Vokoun was rarely tested, but he couldn't afford a slip-up in a tightly played defensive struggle. After playing the previous four seasons with Florida, the 35-year-old goalie left for the Capitals after failing to reach a contract agreement with the Panthers over the summer.

"It's my old team, so you want to win and you want to play good," Vokoun said. "It wasn't like I was looking at the game and saying, 'I've got to win.' I'd be lying if I said I wasn't happy, but when you win you're happy every time. I was as happy when we beat Ottawa or Pittsburgh."

It was Vokoun's first shutout since April 9, 2011, when he blanked the Capitals for Florida.

"He's pretty solid, and when we did have breakdowns he was there to help us out," Washington coach Bruce Boudreau said.

Pressed into extensive action while Michal Neuvirth works to return from a foot injury, Vokoun improved to 4-0 this season.

He wasn't the only player matched up against his old team. Florida's Matt Bradley and Tomas Fleischmann are former Capitals, along with goaltender Jose Theodore, who watched from the bench for the first time this season.

Jim Rogash / Getty Images The Week in Sports Pictures The nation grieved for those hurt, killed and affected by the Boston Marathon bombings. After one of the suspects was caught on Friday — following a day-long lockdown and manhunt — sports returned to Boston over the weekend.

"We worked hard, but the only thing we had were chances from the side," Fleischmann said. "A good goalie like Vokoun can always stop those."

Washington and Detroit are the only NHL teams to win all their games thus far. The Capitals' four-game winning streak at home to start the season is also a club record.

Boudreau wasn't exactly in the mood to celebrate Washington's unprecedented start.

"Quite frankly, when it comes to April and May, I'm not going to be able to sit here and say, 'Hey, we were 5-0 and got that record. Isn't that great?' It's not going to really hold a lot of weight," Boudreau said. "It's nice, but it's just a process of getting to where we want to get."

Each of Washington's previous four games were decided by one goal, and three of those went to overtime.

Florida's Jacob Markstrom stopped 29 shots in his first NHL start, but was victimized by Johansson in the first period and by Semin at 1:49 of the third period. Chimera scored into an empty net.

"He had a good solid game for us," Panthers coach Kevin Dineen said of Markstrom. "Not the way you want your debut to go, but he didn't get a heck of a lot of support."

Washington outshot Florida 11-2 in the first period and took a 1-0 lead on a power-play goal by Johansson, whose shot from the right side slipped through Markstrom's pads. Nicklas Backstrom and Alex Ovechkin earned assists.

The Capitals took the game's first nine shots before the Panthers finally tested Vokoun at 11:40 of the period on a blast from the blue line by Ed Jovanovski before a line change.

A few minutes later, Washington held the NHL's top-ranked, power-play unit without a shot while killing an interference penalty against Roman Hamrlik.

Semin all but clinched it with a goal from the bottom of the right circle early in the final period. He scored after taking a lead pass from Mike Knuble.

NOTES: The Capitals recalled G Dany Sabourin from the AHL Hershey Bears as the backup to Vokoun. Neuvirth was scratched. ... Florida was playing its second game in two nights, the first of 14 such back-to-back assignments. The Panthers won 7-4 at Tampa Bay on Monday. ... Washington went 4-0 in 1991 and 1997 before losing.