Manchester United boss Jose Mourinho has confirmed that Antonio Valencia suffered a hamstring injury in the 2-1 win over West Bromwich Albion on Sunday.
The full-back was withdrawn in the 66th minute and replaced by Marcos Rojo as the Reds beat the Baggies at The Hawthorns courtesy of first-half goals from Romelu Lukaku and Jesse Lingard.
Valencia has played in all 18 Premier League fixtures for the Red Devils this term and started his fifth match of December in the West Midlands, prompting Mourinho to blame the injury on the accumulation of games played by his stand-in captain.
Speaking in his post-match press conference, the Portuguese coach told reporters: "This is what I call a December injury. It is an injury of accumulation of fatigue. It is a muscular one. Hamstring. Big, small, medium, I don't know.
"Let's wait [before giving an estimated return date]. I think he is an experienced guy to not let it go to difficult limits. But it is an injury of fatigue. Everyone in the Premier League, especially the ones in more accumulation of cups, European cups, they are at risk."
Valencia has now made 24 appearances for United in all competitions this season, scoring twice.
