Everton boss Roberto Martinez has confirmed Romelu Lukaku suffered an ankle injury in his side's 2-1 victory over Manchester City in the first leg of their Capital One Cup semi-final.
Lukaku, 22, struck his side's winning goal with 10 minutes remaining to help the Toffees take one step into the final. But the Belgium international looked to be struggling in the build-up to his strike, his 19th of the season, and was withdrawn moments after to be replaced by Arouna Kone.
Speaking in his post-match press conference, Martinez said he was unsure if the striker would be fit to return in time for Saturday's FA Cup third round clash with Dagenham and Redbridge, but remained hopeful the injury was not a serious one.
"Romelu will be assessed," Martinez said. "I don't know if he'll be available for the weekend, but I don't expect it to be too serious."
Everton were forced to finish the final five minutes of the match with 10 men when Seamus Coleman limped off after Martinez had already used all three of his substitutes. The Republic of Ireland international is now facing a month on the sidelines with a calf strain.
Tom Cleverley was also withdrawn at half time to be replaced by Leon Osman with the former Manchester United also suffering from a calf problem. "Seamus Coleman's injury is the most serious of the three," Martinez added. "Cleverley had a calf problem that flared up at half-time."
Everton took the lead just before half time when Ramiro Funes Mori was quickest to react and fire home from close range after Willy Caballero saved Ross Barkley's stinging effort.
City wiped out that opener with a fine equalising goal after 75 minutes, springing forward on the counter before Sergio Aguero teed up Jesus Navas to score his first City goal since September 2014.
The home side took the lead again just minutes later, however. Gareth Barry's superb cross from the left found Lukaku who snuck in-between Nicolas Otamendi and Martin Demichelis to power a header home from close range.
Everton will take their slender advantage to the Etihad Stadium for the second leg on 27 January.