The Blues right-back is still struggling to shake off the thigh injury which forced him to miss the second half of the home game against Norwich City two weeks ago.
Despite managing just forty-five minutes against the Canaries, Melchiot did appear in the game at Arsenal last weekend but was again forced to retire nine minutes from the end of the 3-0 defeat at Highbury clearly still struggling with the thigh strain.
The loss of the Dutch international would come as a big blow to manager Steve Bruce as Melchiot has made the right back position his own by starting every game in that position since the beginning of the season.
Bruce will have to choose either Olivier Tebily, Martin Taylor or even drop Damien Johnson back to the right-back spot should Mario, as now seems likely, fail to shrug off the injury in time for the match at Villa Park on Sunday lunchtime. My guess is that he'll go for the latter option.