Perth boss Tommy Wright was forced to defend his selection policy following Saturday's 2-1 Scottish Premiership defeat to Celtic.
Four-goal May started the match on the bench but his second-half introduction coincided with a marked improvement in Saints' play as they pushed the Glasgow giants close at the death.
Wright claimed MacLean has already shown, against Norwegian big guns Rosenborg in the Europa League qualifiers earlier this season, that he has the strength to lead the attack as a lone forward against stronger opposition.
But now the former Sheffield Wednesday and Aberdeen striker admits May is already showing the type of form which means he may have to let his young apprentice take over against sides like Celtic.
He told Press Association Sport: "It all depends how the gaffer depends to play. I'm sure Stevie can play that role himself.
"I think Stevie and I have shown with the second-half performance at Celtic that we can play together. I can drop a bit deeper and help the lads out in midfield.
"If we play one up front Stevie is good enough to play as the lone striker and I can play further back.
"I'm sure the gaffer knows that now as well. When we played Rosenborg at home and Stevie scored in the 1-1 draw that took us through, we proved we can play together against the top sides.
"It really all depends what the gaffer is planning and it might end up being me who starts on the bench. He will make the decision and whoever is left out will just have to get on with it."
The two are likely to be reunited in a two-pronged attack on Tuesday, however, as Saints travel to Hamilton for their Scottish League Cup third-round meeting at New Douglas Park.
Accies are flying high in the second-flight but player/boss Alex Neil insists his side go in to the match as underdogs.
He said: "This is a game that we can enjoy as there is no pressure on us.
"We are top of the Championship and beat Kilmarnock in the last round but St Johnstone are a well-established Premiership side who were playing in Europe recently. They are favourites but we will give it a go."