The midfielder suffered a broken tibia in his right leg as a result of a late tackle by Hugh Murray back in Morton's 3-1 home win over Partick Thistle on 6 October last year.
Stirling, 23, had just been finding his feet as a full-time professional and showing signs he could be an influential signing but he failed to recover in time to feature again before the campaign ended.
Allan Moore told the Tele: "Stephen is one we'll have to monitor over the summer and see how he is and if he wants to come back in for pre-season.
"He'll need to come back in for pre-season to prove himself all over again because it's an injury he's still to fully recover from.
"He's not been back in full training or anything, so there's nothing I can judge him on.
"I can't judge him on what he did before he got injured.
"So we've left the door open for Stephen.
"I'll need to see how he is when he comes back in and I think he understands that."