Clint Mathis injured his right knee during training with the U.S. national team on Tuesday afternoon, prompting Coach Bruce Arena to call in Miami midfielder Pablo Mastroeni for Thursday’s international friendly against Ecuador. According the Associated Press, Mathis went down with five minutes left in the second training session of the day and yelled, “My God, I’ve torn my ACL.” An MRI performed this morning in Columbus, Ohio confirmed that Mathis suffered a complete tear of the ACL. Mathis is scheduled to have surgery some time in the next two weeks, after the swelling in his knee has subsided sufficiently. The surgery will be performed by U.S. national team doctor Bert Mendelbaum. Mathis is expected to be out of action for at least the next six months. “This injury is kind of tough to deal with, (but) it’s something that we deal with in soccer,” said Mathis, who also tore the ACL in his left knee as a sophomore at the University of South Carolina in 1995. “It’s part of the game. It was kind of a freak thing, but it’s a situation where I’ll go out and get the surgery and work hard to get back. “Hopefully, I’ll become a better player out of this. Everything happens for a reason. You’ve just got to move on and deal with it.” He reported problems in his left knee at the beginning of 2001 and elected not to have surgery after receiving a second doctor’s opinion that it was unnecessary. The USA plays Jamaica June 16, Trinidad & Tobago June 20 and Mexico July 1 in qualifiers. With Josh Wolff recovering from an ankle injury and Cobi Jones suspended for the first two (unless U.S. Soccer’s appeal is granted), Arena faces a dearth of attackers. Landon Donovan leaves this weekend to play with the U-20 national team at the World Youth Championship, which could keep him occupied until early July. Forwards Joe-Max Moore and Brian McBride, who missed the previous qualifiers through injury, are back in action and in camp for the Ecuador game. Mastroeni, a native of Argentina, grew up in Arizona and recently became a U.S. citizen. The defensive midfielder is in his fourth season with the Miami Fusion. He participated in a U.S. national team training camp earlier this year in January.