Blackburn boss Mark Hughes has admitted the loss of Morten Gamst Pedersen for potentially the most crucial week of the club's season is a major blow.
Norway international Pedersen returned with a hamstring injury from Wednesday's friendly against Croatia and will now be ruled out for up to two weeks.
It means Pedersen misses tomorrow's Premiership trip to Everton, next week's UEFA Cup clash with Bayer Leverkusen and the FA Cup fifth-round clash against either Arsenal or Bolton.
Hughes said: 'Morten is a big part of what we do, not only with the tempo of the team but his set-plays. He is going to be a big loss, and to lose him this week is hurtful to us.'
Rovers will also be without the suspended Stephen Warnock for the trip to Goodison Park - which comes a month after their storming 4-1 win over David Moyes' men in the FA Cup third round.
Blackburn defender Ryan Nelsen - himself recently back from a serious hamstring strain - has warned his side to brace themselves for a much sterner test.
Nelsen said: 'Knowing David Moyes' team, I presume it will still be in the back of their minds. I think the players' pride got hurt a bit, so it will be very difficult.'
Nelsen is relishing his return to the Rovers' line-up, the Everton clash his fourth comeback game after a long and frustrating period on the sidelines.
He is already showing signs of developing a solid centre-back partnership with African Chris Samba, who impressed in Rovers' win over Sheffield United last week.
Nelsen said: 'I am feeling a bit rusty but I am really enjoying being back and involved. It was just a case of keeping busy and trying to get myself as fit and strong as I could.
'I think Chris did extremely well last week, because Sheffield United are an awkward team to play against. For a young man in his first Premiership game, I don't think we could have asked any more of him.'
Meanwhile, Nelsen has admitted the loss of Pedersen for such a crucial period in the club's season will be a major blow - given the Norway international's current form.
Nelsen added: 'Morten can be quiet for long periods, then pull off what the average person can't do. It is a credit to his ability, and you can't put a price on match-winning things like that.'