It's unclear just how bad Diego Costa’s injury is - he may well be involved against Everton on Saturday - but his absence would be a big blow for Chelsea.
Chelsea lost at Everton last season when they weren’t at their best and missed a lot of chances, so this fixture is the sort of match they recruited Costa for.
Costa has already shown glimpses of what he can bring to Jose Mourinho’s team. He scored against Leicester when Chelsea were going nowhere fast and at Burnley he got them back into the equation after Scott Arfield’s surprise opener.
Whether he recovers in time to play at Goodison Park or not, this injury he has is a worry.
Costa had a problem with his hamstring at the end of last season and only managed a few minutes in the Champions League final for Atletico Madrid, while he didn’t look fit to me when he was playing for Spain in the World Cup. And now he’s got a hamstring issue again.
We’ve seen in the past how hamstring injuries can affect players and if Costa keeps pulling his hamstring it will start to affect him mentally, affect how he runs and he won’t trust himself to explode into a sprint.
It could become a long-term problem – but obviously Chelsea will hope that’s not the case because he’s made a difference to their team and I'm sure Jose Mourinho is doing all he can to get him ready for Saturday night.
Fernando Torres is in talks with AC Milan so he might be out of the frame to play in Costa's place – although he probably wouldn’t be the answer anyway – and that means Didier Drogba could be set for a start if Costa doesn't make it.
I’m sure he didn’t imagine that happening just three games into the season after returning to Chelsea in the summer!
Drogba scored a great dipping volley at Goodison Park a few years ago and it will be interesting to see how he gets on if he is selected.
I’m also looking forward to seeing what Romelu Lukaku does. There’s no love lost between the Everton forward and his former manager Mourinho and I’m sure he’ll be fired up to do well against his old team.
Lukaku up against John Terry and Gary Cahill will certainly be worth watching on Saturday night!
Meanwhile, Steven Naismith has been a real unsung hero for Everton so far this season. He got the winning goal in this fixture last year and has been involved in a lot of the good things Everton have done this term.
I’d be surprised if Samuel Eto’o – another player who has had his run-ins with Mourinho in the past – makes his Everton debut but the key could be at the other end of the field.
Everton have conceded four in their first two and, although the goals they’ve let in wouldn’t necessarily concern me, the fact they have surrendered a lead three times in two Premier League games this season is a worry.
Everton were 1-0 and 2-1 up at Leicester and two goals to the good against Arsenal last weekend before being pegged back. That can become a bad habit and they need to find a way of shutting games out in those situations.
I think they might concede a couple more this weekend, though – I’m predicting a tight 2-1 win for Chelsea.
Before Costa got injured I was thinking this was a banker for Chelsea but it has become a lot tougher to call now we're not sure whether he'll play.
I’m still going for a Chelsea win – the likes of Cesc Fabregas have been fantastic for them so far – but I expect Roberto Martinez and Everton to make life difficult for them.
Saturday Night Football: Everton v Chelsea, 4.45pm, Sky Sports 1 HD