MIAMI — This was supposed to be a leaner, meaner Team USA that partook in this second World Baseball Classic. A "team," with all of its positive connotations, that would avoid the slip-ups of its predecessor.

Saturday night at Dolphin Stadium, however, Team USA set a new low for ineptitude. And now its margin of error has been reduced considerably.

Team USA couldn't even make it to the ninth inning in its first game of the second round. Instead, Puerto Rico, supported by most of the 30,595 fans, prevailed 11-1 in the seventh inning by virtue of the mercy rule.

Once Mike Aviles stroked a two-run single off Matt Thornton to put Puerto Rico up by 10 runs in the bottom of the seventh, the game concluded in "walk-off" fashion. The Puerto Rico players stormed the field — surprising many Team USA players, who didn't understand how the rules worked.

"We just got beat down, bad," Team USA rightfielder Adam Dunn said. "It's embarrassing."

On Sunday night, Team USA will be playing for its life against Team Netherlands, the darlings of the event, which lost Saturday's opener to Venezuela, 3-1. The loser of the game will be sent home, as per the WBC's double-elimination format. The winner will survive until Tuesday to play the loser of Monday night's game between Puerto Rico and Venezuela.

"It's baseball," Derek Jeter said. "Anything can happen. Look at what happened to the Dominicans (who were eliminated in the first round after losing twice to the Netherlands). Look at what happened to us last time."

Team USA didn't make it out of the second round in 2006, and its short run stood out not only for poor play on offense and defense, but also for poor game management and a failure to comprehend the WBC's unusual rules. For instance, the team struggled to grasp how it could be eliminated by the now-defunct run-differential rules.

Manager Davey Johnson, who wound up managing the game after announcing Friday that he would not be here — his stepson's wedding "got over early," he explained — left starter Jake Peavy in the game even though Puerto Rico pounded Peavy for six runs and six hits in only two innings.

"Just basically let him get a little more work," Johnson said. "Unfortunately, it wasn't really great work, but he still needed the work."

And when Puerto Rico, up 9-1, put the winning run on second base in the seventh after Felipe Lopez doubled to move Geovany Soto to third, Team USA didn't play the game any differently.

Jeter said he knew the game would end if Puerto Rico took a 10-run lead. He appeared to be in the minority.

Asked when he knew the game had ended, catcher Brian McCann said, "When they all ran out of the dugout."

Mark DeRosa answered similarly, noting, "When you put this uniform on, you don't expect that to be a part of it."

Said Johnson: "At that point, we were eight runs down. I don't usually make pitching changes just to avoid the 10-run rule."

The Mets' Carlos Beltran homered, singled twice, scored three runs and drove in two for Puerto Rico. Mets teammate Carlos Delgado had a single and two RBIs. Winning pitcher Javier Vazquez, the former Yankee, pitched five innings, allowing a run and four hits.