Team USA (0-1) never recovered after Dickey's early struggles, managing six singles among its eight hits while stranding eight runners in opening the WBC with a dud.
The U.S. team has been so-so thus far in the WBC, getting past the round-robin stage but stalling out in the semifinals the first two times, helping to clear the way for Japan to win the first two titles.
Team USA is stocked for a good run in this year's tournament, trotting out a lineup that includes three former league MVPs Ryan Braun, Joe Mauer and Jimmy Rollins along with nine other players who have been major league All-Stars.
Hoping to get the tournament off to a good start, manager Joe Torre handed the ball to Dickey, the reigning NL Cy Young Award winner and the first knuckleballer to win the prize.
While many of the big-name pitchers back out of playing in the WBC, Dickey was an enthusiastic participant, in part because he was on the 1996 U.S. Olympic team that earned a disappointing bronze.
His opening game in the WBC didn't go too well.
Mexico jumped on the right-hander's knuckleball right off, starting with Eduardo Arredondo's reach-and-slap single to open the game. He came around to score on Cruz's sacrifice fly after a double by Ramiro Pena. Gonzalez made it 2-0 with a groundout to second, revving up the crowd.
Gonzalez brought fans to their feet in the third inning with a two-run homer to the deepest part of the park, a towering shot above the pool deck in right-center that was upheld by a video review.
Dickey was three pitches short of the WBC minimum 65 after four innings and didn't come back out. He allowed four runs and six hits.
Mexico was in need of a lift after a disappointing opening game against Italy.
Leading 5-4 after eight innings, the Mexicans lost 6-5 after Sergio Romo, closer for the World Series champion San Francisco Giants, gave up a two-run double to Anthony Rizzo. Mexico had the bases loaded in the bottom half against Jason Grilli, but Jorge Cantu grounded out to end the game.
For their critical second game, Mexico turned to Gallardo, the Milwaukee Brewers ace who won 16 games last season.
Unlike Dickey, he was sharp early, facing the minimum through three innings after Mauer singled in the second inning and was quickly erased on a double play.
Gallardo was done after a leadoff single by Rollins in the fourth inning and a one-out walk to Braun. David Wright followed with a run-scoring single to right off Luis Mendoza to cut Mexico's lead to 4-1, but Eric Hosmer grounded out on a comebacker with runners at the corners to end the inning.
Gallardo allowed a run on two hits and struck out four.
Cruz put Mexico up 5-1 with a sacrifice fly off Glen Perkins in the fifth after Arredondo's third hit led off the inning.
Team USA had two on in the fifth and sixth innings and failed to get a run in, and Rollins was stranded at second in the seventh after a two-out double, their first extra-base hit of the night.
The U.S. finally came through in the eighth, when Hosmer blooped a single to center off Fernando Salas to score Braun and cut Mexico's lead to 5-2.
Romo bounced back from his rough outing against Italy, closing out Mexico's statement win with a perfect ninth that set off a huge roar inside Chase Field and sent the Mexican players charging off the bench.
World Baseball Classic
• Puerto Rico 3, Spain 0
• Dominican Republic vs. Spain, 9 a.m.
TV • MLB Network
• Puerto Rico vs. Venezuela, 3:30 p.m.
TV • MLB Network
• Italy 14, Canada 4
• Mexico 5, United States 2
• Canada vs. Mexico, 12:30 p.m.
• United States vs. Italy, 7 p.m.
TV • MLB Network