San Jose completed a season sweep of the Blues, winning all three games by a combined 16-7. St. Louis has lost two in a row after winning eight of 11.
Matt Irwin, Brent Burns and Marty Havlat added goals for the Sharks, who led 3-0 after 22 minutes. Niemi improved to 18-6-6. Kevin Shattenkirk and Jay Bouwmeester scored second-period goals for the Blues.
The Sharks jumped to a 2-0 first-period lead on goals by Pavelski and Irwin in a span of 2:56. Both came from close range on rebounds of missed shots that caromed off the end boards.
Pavelski scored his 13th after a miss by Havlat, and Irwin jumped on a misfire from Justin Braun for his first of the season.
St. Louis goalie Jaroslav Halak gave up three goals on the first 12 shots he faced and fell to 16-6-2.
The Blues climbed to 3-2 on Bouwmeester’s goal with 24.2 seconds left in the second period. Havlat pounced on a rebound with 11:41 left in the game to make it 4-2.
San Jose won the earlier meetings 6-2 and 6-3.
NOTES: San Jose has outscored its opponents 44-15 in the first period this season. .... Blues coach Ken Hitchcock celebrated his 62nd birthday. ... St. Louis C David Backes missed his first game since Jan. 25, 2010, a string of 274 successive regular-season appearances. He sustained an upper-body injury in a collision with Ottawa C Colin Greening on Monday. Backes, who has 16 goals and 14 assists in 32 games, is expected to be out at least a week. ... The Blues were also without LWs Jaden Schwartz and Vladimir Sobotka, who missed the game with upper-body injuries. Backes, Schwartz and Sobotka have combined for 29 goals and 38 assists. ... The Sharks are 0 for 16 on the power play over their last seven road games.