Manchester United's top scorer Romelu Lukaku could return for the FA Cup clash on Friday, boss Jose Mourinho said on Monday, after initially ruling him out for a week.
The Belgian forward, who has scored 15 times this season, had played every minute in the Premier League before being taken off on a stretcher against Southampton on Saturday following a clash of heads with Wesley Hoedt.
That ruled Lukaku out of Monday's trip to his former club Everton, and speaking before the game Mourinho told Sky Sports: "I would say a week [out for Lukaku]. It's nothing really important -- just a little protection, but no problem."
But Mourinho revised his timeline after beating Everton 2-0, saying that Lukaku could return for the FA Cup third-round tie with Derby on Friday.
"Romelu is not a problem," Mourinho said. "Maybe Romelu can play [against Derby]. It was precaution by the doctor, it was following the rules to protect the situation but Romelu was in the dressing room, never lost memory, he knew what happened.
"He didn't come today to follow the protocol but he wanted to play. We had to stop him to play because he was saying, 'I feel amazing, I should go and play' but to follow the protocol and also to protect the player, we decided not to play [him].
"Probably Romelu [is] back [against Derby]."
There are 10 days between Derby's visit to Old Trafford and United's Premier League home clash with Stoke, when Lukaku should be fully fit.