The Paisley men produced heroics at Hampden in the Scottish Communities League Cup semi-final to edge Celtic out in a five-goal thriller and book a final place against Hearts next month.
They also face a rematch with Neil Lennon's men on Saturday, this time in the quarter-finals of the William Hill Scottish Cup quarter-final.
But Saints have now failed to find the mark in 298 minutes of SPL action. Their last goal came in the 2-1 home success over Inverness on January 30.
With tomorrow's visit of a Hearts side in freefall and just one point above them looming, the teenager has pinned hopes of a league revival on a victory over the side they'll face at the National Stadium next month.
McGinn said: "The Hearts game is massive and what we have to do is just concentrate on the next game and not let the cup ties distract us. The losses in the league have been disappointing. Hearts are above us in the league so we have a great chance to climb above them.
"Although we are nine points off the top six, we have a game in hand.
"So it is not beyond us to get back in there if we can string some positive results together.
"We have a cup final coming up, though, and everyone is desperate to play in that. The only way to guarantee that is to make sure that you are doing it in the SPL.
"We have home advantage and it is vital that we make the most of that. We have already beaten Hearts on their first visit to St Mirren Park earlier in the season, so we know we are more than capable of taking three points tomorrow."
The 18-year-old is of course the youngest grandson of Jack McGinn, the former chairman of Celtic in the 1980s and 90s, who went on to become president of the SFA.
Ironically, the young midfield ace made his St Mirren debut in a 5-0 home defeat by Celtic back in October, but played a starring role in Saints' success over the Hoops in the League Cup semi-final.
He said: "It's been a fantastic season for me so far. To have made my debut against Celtic and then play in the St Mirren side that beat them in the League Cup semi-final was amazing, I will never forget it.
"We have them on Saturday coming here in the Scottish Cup and they will be looking for revenge, but all our focus has to be on Hearts right now."
McGinn has also thanked Buddies skipper Jim Goodwin, former Scotland ace Gary Teale and strike talisman Steven Thompson for their role in helping him develop on the field.
He said: "I am really lucky that we have guys like Jim, Gary and Stevie who have so much experience.
"We have a great team spirit at the club and that will be key in helping us get the result we need tomorrow.
"The SPL is so tight and there is very little between the teams. It all comes down to who wants it most. Against Hearts we have to make sure that is us."