Fulham will be without Bryan Ruiz for at least four weeks after the Costa Rica midfielder aggravated his already injured hamstring.

"He was in the final stage of his rehabilitation and he aggravated his hamstring muscle again," Fulham manager Martin Jol said.

Ruiz, who was signed from FC Twente, will be sent to Germany to see a specialist.

"Hopefully, he will be fine," Jol said. "But of course, it's a big disappointment because Bryan is a vital player for us."

Fulham haven't scored and have lost twice in the three games that Ruiz has missed.

He had been slated to play Monday, when Fulham hosts Newcastle.

Ruiz, however, should be ready for Costa Rica's World Cup qualifiers in February.