PHOENIX -- The country where hockey is king stole America's pastime on a chilly Arizona afternoon.

Adam Stern, a young backup outfielder for the Boston Red Sox, hit an inside-the-park homer, drove in four runs and made two sensational catches in center to lead Canada over the United States 8-6 Wednesday in the World Baseball Classic.

"We were definitely pumped up to play this team," Stern said.

Jason Varitek's 448-foot grand slam helped bring the United States back from an 8-0 deficit, but a Canadian team made up largely of minor leaguers held on.

"It's a very quiet locker room right now," U.S. manager Buck Martinez said. "I think everybody is feeling like they got kicked in the stomach."

Chase Utley thought he had given the United States the lead in the eighth, flipping his bat and raising both arms in triumph after he hit a long drive to center with two on. But Stern made a leaping catch at the wall near the 407-foot sign to end the inning.

"I thought Chase's ball was gone when he hit it," teammate Derek Jeter said. "I mean, he crushed that ball, but you've got to hit it pretty good to get it out in that part of the park."

A crowd of 16,993 at Chase Field alternated between booing America's futility and supportive chants of "U-S-A!"

The United States (1-1) must beat South Africa on Friday or have Mexico lose one of its remaining games to stay alive in the 16-nation tournament.

If Mexico, Canada and the United States finish 2-1, the tie would be broken by fewest runs allowed per inning in competition involving only those three teams. In that case, the United States would advance if Mexico scores at least three earned runs against Canada on Thursday.

Canada (2-0), which had to rally in the ninth Tuesday night to beat South Africa 11-8, hit Dontrelle Willis hard and scored in each of the first five innings.

"I just didn't do anything right today," Willis said. "It's just one of those games."

Stern tripled in a run in the second and singled in two more in the third. Then leading off the fifth, his opposite-field fly ball skidded off the base of the bullpen fence past left fielder Matt Holliday.

As Holliday pulled up lame, Stern raced around the bases for an inside-the-park homer to put Canada up 8-0. After being examined by the trainers, Holliday stayed in the game.

Michael Young started the six-run U.S. fifth with a leadoff single, then scored from first on Ken Griffey Jr.'s second double. Derrek Lee's single brought in pinch-runner Jeff Francoeur. Chipper Jones singled, then Vernon Wells drew a two-out walk that loaded the bases.

Eric Cyr relieved Chris Begg for Canada, and Varitek drove a 2-1 pitch over the main concourse walkway in left-center, cutting the lead to 8-6.

Canada threatened in the eighth when Ryan Radmanovich walked and tried to score from first on Morneau's double to right. But Utley took the relay from Francoeur and threw out Radmanovich at the plate to end the inning.

Adam Loewen, a 21-year-old left-hander who pitched last season for Class A Frederick in the Baltimore organization, gave up three hits and walked three but didn't allow a run in 3 2/3 innings and got the victory.

The United States didn't allow a runner beyond first base in its 2-0 victory over Mexico on Wednesday, but Willis was ineffective and allowed five runs and six hits in 2 2/3 innings. He was relieved by Al Leiter, who surrendered two runs on three hits in two-thirds of an inning.