Madrid - Portugal and Valencia forward Goncalo Guedes will have surgery on a groin injury on Friday and could be out of action for up to two months, the La Liga club announced on Wednesday.
The 22-year-old, who joined Valencia from Paris Saint-Germain in the close-season after a successful campaign on loan at the Mestalla last season, has been struggling with a pubalgia, commonly known as a sports hernia.
His form has dipped this term, failing to score in 14 appearances.
Marcelino's Valencia have been disappointing so far this season, having finished fourth in La Liga to qualify for the Champions League seven months ago.
They sit 15th in the Spanish top flight after winning just three of 15 matches, and will drop into the Europa League last 32 after a Champions League group-stage elimination.