The Sharks, who entered the day tied for fifth in the Western Conference after a recent slump, sent left wing Ville Nieminen, college forward Jay Barriball and New Jersey's first-round pick, which they acquired last year, to the rebuilding Blues.
Guerin revitalized his career in his first season with St. Louis, scoring 28 goals and 47 points in his 14th NHL campaign. The bruising power forward waived his no-trade clause to leave the Blues for the Sharks, who expect to contend for a Stanley Cup championship.
"I'm thrilled," Guerin said. "This is one of those teams that was on my radar. I am very happy to be going there. You have certain expectations and places that you want to go, so it was easy (to agree to the trade). When it was presented to me, it was a no-brainer."
Two days earlier, the Sharks acquired veteran defenseman Craig Rivet from the Montreal Canadiens for defenseman Josh Gorges and their own first-round pick. The moves signal a change in philosophy for Sharks general manager Doug Wilson, who gave every opportunity to his rich stable of young talent.
But San Jose's youth has been evident in an inconsistent season despite the club's impressive overall record. The Sharks, who lost 3-2 to Anaheim on Monday night, have lost four of six to slip into a second-place tie with Dallas in the Pacific Division.
With NHL leader Nashville acquiring Peter Forsberg and Detroit adding Todd Bertuzzi, the Sharks apparently felt they had to make a move to keep up.
So Wilson used San Jose's stockpile of draft picks and prospects to add two playoff-tested veterans for the season's final 19 games _ even if they're only rentals. Both Guerin and Rivet can be unrestricted free agents after the season, but Guerin has won a Stanley Cup with New Jersey, and Rivet has been a solid contributor to the Canadiens for 11 seasons.
The 36-year-old Guerin, who is making just $2 million on a one-year contract this season, will be the Sharks' oldest player _ more than 3 years older than Rivet. Guerin also played with Sharks center Joe Thornton for most of two seasons in Boston.
The Sharks acquired Nieminen last season from the New York Rangers, but the Finnish forward has been in coach Ron Wilson's doghouse all season.