Capitals goalie Tomas Vokoun, left, allows four goals against the Sharks, including this one by Jason Demers during the second period. (Marcio Jose Sanchez/Associated Press)

The Washington Capitals arrived here riding their longest winning streak since October but just like they have on every visit to Northern California over the past 18 years, they will leave with a loss.

Washington fell, 5-2, to the San Jose Sharks Saturday night at HP Pavilion, snapping a four-game winning streak and extending the team’s road woes as it dropped its fourth out of five away from Verizon Center.

It was a contest where each mistake by the Capitals, from defensive breakdowns to turnovers and costly penalties, seemed to result in a goal for the Sharks. Perhaps no mistake was more glaring than when a lapse in defensive zone coverage on the shift immediately following a goal allowed San Jose to regain control.

Patrick Marleau recorded the game-winner in the third period just 16 seconds after Washington tied the score to knock the wind out of the visitors as they tried to scramble back in the contest.

“It was 2-2, it was a game and usually whoever gets the next one has a good chance of winning,” Capitals Coach Dale Hunter said. “It ended up we broke down in our own end and it cost us. We just tied it up and they come back but we made a few mistakes and it cost us.”

In addition, Mike Green, who had only just returned on Tuesday after missing 23 consecutive games with a strained right groin muscle, left the contest in the second period with tightness in his groin. Green saw only 7:11 of ice time on nine shifts before leaving the game.

“It got a little tight, so we’re being careful with him and we pulled him out,” said Hunter, who added that Green’s removal was not related to a crushing check the defenseman absorbed from San Jose center Andrew Desjardins early in the period.

The Capitals were already without top center Nicklas Backstrom.

As for the game, Marleau and Dan Boyle each finished with three points while Sharks netminder Antti Niemi finished with 28 saves to continually frustrate the Capitals, who were held to less than three goals for the first time in five games.

For Washington, Dennis Wideman and Joel Ward each recorded goals while Tomas Vokoun wrapped up the night with 34 saves in an outing where he was plagued by constant run-ins with the Sharks, who weren’t afraid to make contact with the veteran goaltender in his crease.

The Sharks’ surge didn’t come until after a scoreless first period, which marked the seventh consecutive road game that Washington has failed to score in the opening frame.

Only 5 minutes 15 seconds into the second, a point shot by Jason Demers bounced off the lively end boards, ricocheted off Vokoun’s leg and then trickled over the goal line to give San Jose a 1-0 lead.

Washington fought back quickly. On the first power play of the game, with Brad Winchester in the box for goaltender interference, a series of pretty passes resulted in a backdoor one-timer for Wideman to tie the score at 6:37 of the second.

Despite evening the contest, the Capitals appeared to be wearing down under the weight of San Jose’s relentless forecheck. Washington’s passes in its own zone weren’t crisp, players lost track of coverage assignments and allowed the Sharks to fire seemingly endless rounds of shots.

“It was hard [with five defensemen once Green left] we were pretty tired I felt in that game, double shifting and changing up against lines you were playing against,” said Karl Alzner, who finished with 24:10 of ice time. “It was tough to play but it’s going to happen sometimes.”

With less than a minute left in the period, Wideman was called for high sticking and San Jose didn’t need any more of a nudge to pull ahead. Defenseman Brent Burns fired a heavy point shot past Vokoun, who was being screened by Marleau on the play, that put the Sharks in front 2-1 with only 8.2 seconds left before the intermission.

The Capitals managed to bounce back just 44 seconds into the third when Ward recorded his first goal since Nov. 11 to make it 2-2. After Ward’s first tally in 25 games came perhaps the most costly error.

San Jose’s top line abused Washington on the ensuing shift as Joe Thornton made a behind the back pass to an unguarded Marleau to regain the lead at 3-2 just 16 seconds after allowing it to escape.

Marleau’s tally appeared to demoralize the Capitals, who haven’t been able to put forth consistent, 60-minute showings on the road much this season and are now 7-11-1 away from home. Tallies by Marc-Edouard Vlasic and Torrey Mitchell (empty net) provided the game’s final margin.

“I think we make bad turnover in our zone at the blue line, puck was coming too slow for the point and I don’t have time to react,” said Alex Ovechkin, who finished a minus-3 with three shots in 21 minutes of ice time. “We can’t do that in our zone that kind of mistake is going to cost us a win.”