Mitchell has been out of action since the February Scottish Cup fifth-round victory over Arbroath but could be included in the matchday squad while McGregor has been missing the last few weeks as well.
“Demetri has been back in training for a couple of days so it’s great to have him back in the squad,” the caretaker manager said.
“We’ve also got Darren back, and it’s good that we’re getting some bodies back into the group at this time of the season; it will help lift the players and keep competition for places.
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“I think it’s important to have people like Daz involved on matchdays, as he’s such a big personality, a leader, a model professional, and he’s a big asset to have at the club.”
James Scott is fit after limping off towards the end of the victory over the Buddies but Chris Cadden won’t be available after picking up an injury that forced him off midway through the first half at the SMiSA Stadium.
“Cadds won’t be available, the game has come a little bit soon for him,” Gray confirmed.
"His thigh has settled down quickly, which is really positive, but we will see how he goes moving forward.
“James had a little bit of cramp and fatigue because he’s not played many minutes, so to go and put two big shifts in back-to-back was great for him. He’s trained all week and is absolutely fine.”