Alonso said that the winger would be out for “a few weeks” when he spoke shortly after.
Meanwhile, Emegha has yet to play for Chelsea in a competitive match since arriving from BlueCo sister club Strasbourg in the summer in a switch that was first agreed last year.
He started pre-season well and scored in back-to-back behind-closed-doors friendlies against Crawley and Bromley at Cobham, but picked up a hamstring injury against the latter.
Emegha has not featured since, though was an unused substitute during the Carabao Cup win over Luton back in August.
The Dutch striker has been spotted in training footage and pictures released by Chelsea this week, be he will not be involved against Everton on Saturday.
“He's not yet [available].” Alonso said of Emegha. “He felt something [on Thursday], a little thing.
“He's going to be training next week but he's still not 100 per cent fit to be playing in the game.”
Asked what the 23-year-old striker will offer when he is available, Alonso replied: “When he's fit, he is very special because he's 195 centimetres (6ft5in). He's quick, he attacks the space, he's a threat.
“So he needs to be fully fit and at this moment he's having little things and unfortunately he's not been available. But we are looking forward to that. He feels good and he can help the team but he's going to be difficult for the defenders when he's in good shape.”
Pressed for an update on when Gittens will be returning, the Chelsea manager said: “Not yet. But it's still a few weeks. Still a few weeks.”