SCOTTSDALE, Ariz. -- Anthony Rizzo thought he hit a homer. A sacrifice fly, at least.
He got neither and still sent Italy to its biggest win in three years of the World Baseball Classic.
Rizzo hit a two-run double off San Francisco Giants closer Sergio Romo in the ninth inning, Jason Grilli escaped a bases-loaded jam in the bottom half and Italy rallied to beat Mexico 6-5 in the opening game of Pool D in the WBC on Thursday.
The Italian team got a break when Mexican left fielder Edgar Gonzalez couldn't handle Rizzo's flyball in the sunlight at Salt River Fields.
"I talked to some of the guys that played before for Italy and they said the energy is unreal," Rizzo said. "Today, right out of the gate was unreal."
Italy won the European championship last year, but had struggled in the WBC, failing to get out of the first round each of the previous two tournaments in 2006 and 2009.
The Italians gave themselves a good shot at getting through this time with a strong start and an even better finish against the closer for the defending World Series champions.
Italy scored two runs in the first inning and got a two-run homer for Drew Butera in the fourth to tie the game at 4-all.
Trailing 5-4, Italy faced the daunting task of rallying against Romo, who got the final out in San Francisco's second World Series in three years last season.
Romo got the first out, but Nick Punto hit a one-out double and Chris Denorfia followed with a hard single to left. Romo still appeared as if he would get out of it after two quick strikes on Rizzo, but the Chicago Cubs' starting first baseman hit a fly ball to the warning track, far enough to at least score the tying run.
"Our left fielder was able to get to it, he just wasn't able to corral it and finish it off," Mexico manager Rick Renteria said.
It still wasn't easy for Italy after that.
Grilli, the Pittsburgh Pirates' closer, gave up a leadoff single to Efren Navarro and pinch-runner Walter Ibarra moved to second on a sacrifice bunt. Grilli got Ramiro Pena on a soft liner to shortstop and thought he had struck out Luis Cruz on what was called ball four.
Furious about the call, Grilli hit Adrian Gonzalez with a pitch to load the bases and get the pro-Mexico crowd on his feet.
Grilli gathered himself, though, and got Jorge Cantu to ground out to second, giving Italy a huge win over a Western Hemisphere team.
Nick Pugliese (1-0) allowed no hits in 1 2-3 innings for Italy, which plays Canada next.
"This tournament is so special because it's not about one player, it's not about one team, one city," Italian third baseman Alex Liddi said. "It's about an entire country, so when you have a chance to represent your country at the highest level, it can't get any better than that."
Cantu hit a three-run double in the first inning and Eduardo Arredondo caused Italy problems in the early innings, scoring three runs from the top of the order in the first five innings.
But Mexico didn't score another run after the fifth and Romo couldn't hold the lead, putting them in a difficult spot with the United States up next on Friday.
"He was upset as was the full club," Renteria said. "When we came into the clubhouse, these guys take this to heart and you could see the emotion that Italy had when they came out on top as well as the guys coming into (our) clubhouse feeling the pain of that loss."
Italy and Mexico combined for five runs in a 40-minute first inning before settling down in the opening round-robin game at the spring training home of the Arizona Diamondbacks and Colorado Rockies.
Italy jumped on Mexico starter Rodrigo Lopez right away, getting run-scoring singles from Alex Liddi and Mike Costanzo before the right-hander struck out Butera with the bases loaded to end the inning.
Mexico answered in the bottom half against Italian starter John Mariotti, loading the bases for Cantu's three-run double to the gap in right-center.
Pena made it 4-2 with a run-scoring double in the second.
Lopez, a reliever with the Philadelphia Phillies, allowed two runs on four hits in three innings before being replaced by Juan Aceves, who gave up a tying two-run homer to Butera that just cleared the wall in left.
Cruz hit an RBI double in the fifth that put Mexico up 5-4.
Not much happened after that until the ninth, giving Italy an unexpected victory before it faces the Canadians on Friday in a game that was moved to Chase Field due to a threat of rain.
"It couldn't have been a better game the way it ended, how much fun everyone had," Rizzo said.