Portland Timbers forward Jose Adolfo Valencia will undergo surgery to repair damaged cartilage in his left knee and will be sidelined six to 12 months.

Valencia was acquired on loan from Colombian first-division side Independiente Santa Fe as a Young Designated Player, but after an MRI showed the damage, the terms of his deal were amended.

The 20-year-old will stay with the Timbers this season, but he will not count as a Young Designated Player and be placed on the Disabled List, meaning he is not counted against the team's international player allotment, either.

"Our No. 1 priority is ensuring the long-term physical health of Jose. We are pleased to have worked with his former club in Colombia on amended terms of his transfer, considering the circumstances," said Gavin Wilkinson, general manager of the Timbers.

"We are very committed to Jose as a person and as a player, and intend to return to the original terms of his transfer agreement when he returns to full health following rehabilitation."

Valencia was originally signed in December. He will have surgery Monday.

"We feel strongly about our long-term commitment to Jose and see him as a big part of the future success of this team," Wilkinson said.