SANTO DOMINGO, Dominican Republic -- Each inning when Jered Weaver takes the mound, he leans over and scribbles the initials of his deceased grandparents in the dirt.

The tribute became extra special Monday night.

Weaver pitched 7 1-3 impressive innings as the U.S. baseball team disappointed thousands of Dominicans to stay undefeated this summer, winning 2-0 in the Pan American Games.

"It's E-H-H and B-W, for Ed and Helen Hamlin and Beverly Weaver,'' he said. "They died six years ago from old age.

"I've never experienced anything like this before. There were 20,000 fans. This is an experience of a lifetime. You can't beat 20,000 people screaming at you.''

Stanford's Danny Putnam had a single, double and triple for the Americans, a team of college players that improved to 25-0 by winning the highly anticipated matchup against a Dominican team that features 13 former major leaguers.

"It's amazing how much they love baseball and value what their players have done,'' Putnam said.

Weaver (4-0), younger brother of Yankees pitcher Jeff Weaver, was perfect through 3 1/3 innings with three strikeouts, retiring the first 10 batters before allowing a single to left by Luis Polonia in the fourth. The right-hander from Long Beach State has not allowed a run in 40 innings. He said his arm is stronger than it has been in some time.

He gave up one hit, struck out four and walked one before Huston Street relieved after Weaver's 96th pitch. Street earned his seventh save this summer, allowing one hit.

The Dominican fans danced in the stands, tooted horns, pounded drums and wildly waved their country's flag in the capacity crowd of more than 17,000 in Quisqueya Stadium.

But they didn't see the anticipated victory.

Earlier Monday, Nicaragua defeated Guatemala 5-0 behind Cairo Murillo's no-hitter. The right-hander struck out four and walked one, though three Guatemalan players reached base on errors. Cuba defeated Brazil 4-0 in the other game.

U.S. shortstop Dustin Pedroia of Arizona State left in the fifth inning after injuring his left arm when Ramon Espinosa slid into second for a stolen base. Pedroia was replaced by Paul Janish.

Putnam hit a run-scoring double off the wall in left in the first inning to give the Americans the lead against losing pitcher Dario Perez, a 33-year-old right-hander. Putnam, who extended his hitting streak to 14 games and is batting .375 this summer, singled in the third and tripled in the fifth. That chased Perez, who gave way to former major leaguer Yorkis Perez.

Putnam finished 3-for-4.

The second U.S. run came in the ninth when Mike Nickeas walked with the bases loaded.

Baseball is the national pastime of the Dominican Republic, and the country showcased it at the conclusion of the opening ceremony Friday with a spectacular torch-lighting display. Youngster Luis Pujols, dressed in a Dominican baseball uniform, swung at a ball sitting atop of the mini flame carried first by Boston Red Sox ace Pedro Martinez and then Juan Marichal, a former pitcher and the only Dominican in the Hall of Fame.

Pujols' swing triggered a wire extending across the stadium to the games cauldron, and as it was lit, the fans went into a frenzy.

"We were very excited,'' U.S. coach Ray Tanner of South Carolina said, his eyes tearing up. "This is why you put the uniform on. I wish there'd been more people cheering for us. This is what baseball is all about, a nice night and a packed house. There's no place better than the Dominican Republic when it comes to passion about the game of baseball. It's very special.''

Tyler Greene had his 14-game hitting streak snapped.

The Americans have a U.S. national team record 12 shutouts this summer and have not given up a run here. The United States won its first two games against Guatemala and the Bahamas 10-0 and 12-0, respectively.

The game was delayed 16 minutes because the lights along the right-field side went out about 20 minutes before the first pitch.

Dominican national police came onto the field before the final out to maintain order. Rain began to fall just minutes after the game ended.