BY RIDGE MAHONEY Funny things happen when Clint Mathis is on the field. Balls go into the net and opponents stand around wondering what happened. Thanks to his opportunism and one atrocious offside call, the U.S. rectified a poor first half by beating Mexico, 1-0. Mathis has a goal or an assist in seven straight starts, yet a stat just as important is for the seventh time in 10 games this year the U.S. blanked its opponent. Dangerous attackers Francisco Palencia and Cuauhtemoc Blanco weren’t available for Mexico; U.S. leader of the back Jeff Agoos, defensive midfield staple Chris Armas and frontman Brian McBride also sat this one out. Central defenders Eddie Pope and Pablo Mastroeni played with an aggression and fierceness seldom seen last week when Germany routed the U.S., 4-2, in Rostock. They read the play and cut off passes, sometimes pushing well out of their own penalty area to deny Carlos Ochoa or Daniel Osorno or Jesus Mendoza the ball. Pope was especially strong in the air, with his head and the occasional high foot, which earned him a caution. Inevitably, Pope and Mastroeni were beaten to the ball and caught out of position, but seldom did Mexico exploit the openings. Mastroeni’s slick skills rescued the U.S. several times, although he also put his team in hot water with a rash challenge. Richard Mulrooney played the central midfield spot he does for club team San Jose rather than a right-back role at which he has auditioned this year for Bruce Arena. Like many of the Americans, Mulrooney needed 45 minutes of adjustment to a pressuring opponent, fast surface, thin air and raucous crowd. Neither team played well in a rough, disjointed first half ruled by Mexico. It lost a perfectly good goal less than six minutes in when a Braulio Luna cross was headed by Mendoza to the far post for Ochoa to poke into the net. The assistant referee flagged, ignoring Frankie Hejduk on the far side of the field. Luna’s manic charges and dramatic rolls and unique hairdo gave him the image of a Hispanic Carrot Top, and were just as credible. But not until the U.S. matched his savvy and fury did it get into the game. He and Hejduk traded swats and kicks and swear words every chance they got. Greg Vanney played only the first half at left back, spraying a few bad passes and tackling roughly, before leaving with a strained back he’d aggravated. His prospects remain clouded. He did deflect a shot by Mendoza that floated harmlessly to Tony Meola for one of his two saves on the night. When Carlos Llamosa came in Arena changed from a 4-5-1 to 3-5-2. He also removed Ante Razov, whose solo efforts up front lacked impact and initiative in a weak impersonation of McBride. Replacement Josh Wolff, far more mobile and incisive than Razov, thrice threatened the Mexican goal. A clever free kick by Mathis — from a spot he has scored goals and tested keepers many times before — freed Cobi Jones to ring a left-footed shot off the crossbar. For most of the game, though, Jones was ineffective and he nullified a possible opportunity when he scuffed the ball into a pocket of defenders. A spent Landon Donovan seldom got into the flow offensively and he contributed little to the U.S. attacks. The physical demands of club and international play stacked together in recent weeks has drained him. Mathis had a rather quiet matc,h but he was on hand when defender Manuel Vidrio timed his challenge perfectly to dislodge the ball from keeper Oscar Perez. Even then Mathis’ sense of the dramatic came into play, for his first-timer toward a gaping net from just a few yards away glanced off the underside of the crossbar. Like the game itself, the goal was blemished. But like the result, it was also deserved.