Mount had to be substituted in the 16th minute of the group stage opener after he was caught by Francis Coquelin’s robust tackle.
The young forward seemed to suffer an ankle problem and he hobbled off the pitch to be replaced by Pedro Rodriguez.
After a goalless first half, Valencia ended up claiming three points thanks to Rodrigo’s 74th minute goal, with Ross Barkley missing a penalty in the closing stages.
Speaking during BT Sport‘s coverage of the game at half-time, former Chelsea FC star Gudjohnsen said:
“It’s not an easy decision for the referee to make because he has to decide whether he went through to tackle him on purpose or if he slipped.
“It doesn’t look great when you see it in the replay.
“You can see Mason Mount just going over his ankle and he probably ends up with an ankle sprain. Hopefully it’s not so serious.”
Chelsea FC fans will be hoping that the injury is not too serious as the Blues turn their attentions to their home clash against Liverpool FC on Sunday afternoon.
Mount, 20, has made a solid start to the new season for Chelsea FC, scoring three goals in five Premier League games for Frank Lampard’s side.
The forward spend last season on loan to Derby County working under Lampard before the duo both moved back to Chelsea FC in the summer.
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