CHICAGO, United States (AP) — A depleted Mexico squad reached the Gold Cup quarterfinals after capping an unbeaten preliminary stage with a 4-1 win over Costa Rica, which also advanced as the second-place team in Group A.

Andres Guardado scored twice as defending champion Mexico took a 3-0 lead by the 26th minute against Costa Rica yesterday. It was Mexico’s second win since five players were suspended last week for testing positive for the banned substance clenbuterol in results which the national federation is blaming on food contamination.

Mexico finished the group stage with 14 goals from three wins and conceded just one goal: a 69th-minute strike by Marco Urena of Costa Rica.

Costa Rica finished with four points, equal with El Salvador but marginally ahead on goal differential.

“It was easy for Mexico,” Costa Rica coach Ricardo Lavolpe said through an interpreter. “Too simple.”

Goalkeeper Guillermo Ochoa and defender Francisco Rodriguez, both regular starters for Mexico, were among the five players dropped from the squad last Thursday after the positive drug tests.

The Mexican federation has blamed the results on contaminated meat and applied to replace the players, but CONCACAF officials are seeking more information before making a decision.

Coach Manuel de la Torre said Mexico’s goal remains the same, regardless of how many players he has to select from.

“The main objective is to win the Gold Cup,” he said. “This group very much knows what it needs to do to represent Mexico. Whatever situation is presented, the team knows the only way to get where we need to go is on the field.”

Costa Rica, which has made the quarterfinals in the last five Gold Cups, was expected to be Mexico’s toughest opponent in the group stage. But Mexico overwhelmed Costa Rica with its fast-paced, energetic style, much to the delight of the sellout crowd of 62,000 at Chicago’s Soldier Field — overwhelmingly supporting Mexico. Any hope Costa Rica had of an upset win was gone by the 20th minute, with Rafael Marquez (17th) and Guardado (19th) giving Mexico a quick 2-0 advantage.

“It was like a splash of cold water,” Lavolpe said. “We couldn’t react.”

Guardado scored again in the 26th minute with a strike from the edge of the box. Pablo Barrera made it 4-0 in the 38th.

The margin could have even been greater, but Manchester United’s Javier Hernandez missed a shot from close range and Costa Rica goalkeeper Keylor Navas tipped a second-half shot by Salcido over the crossbar.

“It’s true we played a good match,” de la Torre said. “But there is always room for improvement.”

El Salvador finished with a resounding 6-1 win over Cuba, with Rodolfo Zelaya scoring a goal in each half.

Osael Romero, Lester Blanco, Arturo Alvarez and Eliseo Quintanilla also scored for El Salvador, which needed Mexico to thrash Costa Rica in the later match to have any chance of advancing.

Cuba finally got its first goal of the tournament when Jeniel Marquez scored in the 83rd minute. But the Cubans, who were eliminated with the loss, conceded 16 goals in the tournament — the most by any team.

A Cuban player also defected during the tournament, leaving the team hotel in Charlotte, North Carolina.

In an interview aired Sunday on Univision, 30-year-old Yosniel Mesa said he decided before the tournament to defect because he wanted to play professionally, an option not available to him in Cuba.

A 5-0 loss to Mexico last Thursday, Mesa says he climbed down a fire escape ladder and ran to a car where family members were waiting. Mesa was listed as “injured” on Cuba’s team sheet for Sunday’s 6-1 loss to El Salvador in Chicago.