But a medical condition for the 21-year-old could scupper a loan move to the Keepmoat, or at best delay it beyond the start of the season.
Earlier this year, McCoulsky was diagnosed with a heart condition after complaining with chest pains during a loan spell with Newport County earlier this year.
McCoulsky was diagnosed with pericarditis - inflammation of the fibrous sac surrounding the heart, known as the pericardium - and continues to be monitored for the condition.
Without detailing the promising youngster's full situation, McCann revealed any loan deal could not be completed until late in the loan window.
While he will continue to track McCoulsky's availability, McCann says if another option for a forward signing arises, he will have to act.
"I had a conversation with Lee Johnson [Bristol City manager] in the early part of my days here," McCann said.
"It was just speaking to him about Shawn, knowing what he'd done at Newport last year.
"But the boy is having a problem which I don't want to go into, with him not being too well.
"It's something we may look at again towards the end of the window and see how he is.
"But unfortunately, in football it's about timing and if the right one comes up for us before then it is what it is."
McCoulsky scored 11 goals in 35 appearances for League Two side Newport last season. He has made one senior appearance as a substitute for Bristol City after coming off the bench in the League Cup.
McCann remains keen on adding another forward player to his squad and says conversations are ongoing with potential targets.
One option may be trialist Paul Taylor but a groin injury looks to have scuppered his chances of landing a permanent deal.