[MLS] The San Jose Earthquakes may seem to be stacked with midfielders, but one of its cogs in the second half of the 2009 season won’t be available for a while.

Brazilian Andre Luiz, who played seven games after signing with MLS last July, has undergone arthroscopic surgery on his left knee. Knee pain traced to an injury he suffered last season had been troubling him, and surgery performed on the same knee about a month ago failed to correct the problem though at the time it was deemed to be “successful.” The Quakes did not specify how long he might be sidelined.

Andre Luiz played centerback and central midfield for San Jose last season, and in light of his his knee problems the Quakes signed Argentine midfielder Javier Robles this week.

Robles, 25, grew up in the Velez Sarsfield system but has also spent time at Olimpo and Santiago Wanderers in Chile. He scored a goal against the Fresno Fuego in Saturday's exhibition.

Coach Frank Yallop is also giving extensive playing time to former Indiana midfielder Brad Ring, who was selected in the first round of the 2009 SuperDraft but sat out the entire season with a degenerative hip condition.

Ring scored with a 30-yard blast Monday in a 3-0 win against Cal-Berkeley in a scrimmage. Also on the roster are New Zealand international Simon Elliott, recent signing Joey Gjertsen and Portuguese-born Canadian national team midfielder Antonio Ribeiro.

With MLS having pushed back its compliance date from March 1 to sometime later this month, Yallop has more time to sort out his midfield.

San Jose heads to London Thursday to train at the facilities of Tottenham Hotspur, which in October 2008 signed a cooperative agreement with the MLS team.