"I don't want to be short ... but it's not a big concern," coach John Tortorella said after the defending Stanley Cup champions lost 4-1 to remain the No. 8 seed in the Eastern Conference.
Jeff Halpern scored twice and goalie Brent Johnson stopped 42 shots for the last-place Capitals, who finished with a three-game winning streak that included a win over Atlanta that eliminated the Thrashers from postseason contention and clinched a berth for Tampa Bay the previous night.
"We're getting ready for playoffs," Tortorella said. "I'm not going to get too involved in this game. ... We'll be ready to play. We're right where we want to be."
Nevertheless, the Lightning missed out on an opportunity to move ahead of Montreal into the seventh seed. The Canadiens blew a three-goal lead before losing 4-3 to New Jersey on Tuesday night.
Tampa Bay will begin the playoffs on the road Friday night against top seed Ottawa, which won all four regular season meetings between the teams and is 17-2-1 against the Lightning over the past five seasons.
As the No. 7 seed, the Lightning would have faced No. 2 Carolina in the first round. They won five of eight games against the Hurricanes this season.
"You look at the scoreboard most of the night and it didn't look we were going to get any higher," Lightning center Brad Richards said. "It was tough to get the emotions up. We're thinking about Friday and that was it. It was tough all day. It was really tough after we clinched."
Washington's Alex Ovechkin notched his 54th assist of the season on Halpern's first goal to finish with 106 points - the third-highest total by a rookie in NHL history. He also had 52 goals, third-best all-time for a first-year player.
Halpern gave Washington a 1-0 lead midway through the opening period and made it 2-0 with an unassisted goal just 12 seconds into the second period. Ben Clymer and Steve Eminger also scored for the Capitals, who were outshot 43-28.
Tampa Bay tested Johnson all night long, but only got one shot past the Washington goalie - scoring on Ruslan Fedotenko's power-play goal less than five minutes into the second period. Clymer countered 71 seconds later to restore Washington's two-goal advantage.
"Our confidence is higher now," Johnson said of Washington's strong finish. "I wish we could be going to the playoffs right now, to give our guys something to look forward to."
There were times this season when it looked like the Lightning might become the first defending Stanley Cup winner to miss the playoffs since the 1995-96 New Jersey Devils, however they regrouped after a poor stretch following the Olympic break to clinch a berth for the third straight season and the fourth time overall.
John Grahame, whose inconsistency has left the Lightning without a clearcut No. 1 goalie, missed out on an opportunity to tie Nikolai Khabibulin's franchise single-season record of 30 victories (2002-03).
Notes: Lightning LW Vinny Prospal didn't play because of an upper body injury. D Pavel Kubina, who missed three games from March 27-Apr. 3 with a lower body injury, also sat out. ... Capitals D Jamie Heward missed his third consecutive game with an upper body injury. ... The Capitals recalled RW Jonas Johansson from Hershey of the AHL and G Maxime Daigneault from South Carolina of the ECHL.