Rotherham United in the dark over Sean Morrison

The centre-half hurt his calf at the club's Roundwood training ground last Thursday and has missed the last two matches.

The 33-year-old has undergone a scan but boss Leam Richardson is still unable to put a date on the defender's recovery.

“I don't know,” said the head coach following Tuesday night's Championship loss at Coventry City. “Initially, we thought he'd be okay within a week, but as of this morning we're still no clearer.”

Rotherham United skipper Sean Morrison. Picture: Jim Brailsford

One player who is fit again is loanee Seb Revan and Richardson has revealed how the Millers and parent club Aston Villa joined forces to cure the youngster's nerve-related hip ailment.

The 20-year-old, who had to come off against Watford on February 17, received treatment at Roundwood and has also spent time with the Premier League side's medical team.

The left-back has done well for Rotherham this term, racking up 28 appearances either in his preferred left-back role or as a left-sided centre-half or wing-back.

Richardson, who took charge in December, said: “Certainly since I've been in the building I've felt like he's been growing.

“He's been asked to play in certain positions that are foreign to him but he's taken to them great. He's taken on information really well. Being left-footed, he gives us that balance within the team as well.”