The 18-year-old had been on loan at Arbroath last season but following Danny Lennon’s arrival as boss in the summer, the talented teenager has been brought into Saints’ first-team squad.
The creative left-sided midfielder made his first start at Hearts last month after making his debut off the bench in the 2-2 draw at Hamilton.
Now, after pitting his skills against Hoops heroes Cha Du-Ri and Mark Wilson, McLean is hoping he can continue his first-team sojourn against Motherwell this weekend.
He said: “It is fantastic that the manager had enough faith and belief in me to start against Celtic.
“To make my first-ever home start against players of the quality of Mark Wilson and Cha Du-Ri was fantastic and hopefully I have done enough to stay in the side for the Motherwell game.
“The manager was really good with me before the game. He knew it was a big moment for me and he told me just to go out enjoy the game and express myself. That gave me a real lift in that he backed me to do well and to play to my strengths.
“Just six months back I was out on loan at Arbroath playing in the Third Division play-off against Forfar at Station Park, so it has been some transformation for me.
“To be starting games against the likes of Hearts and Celtic is unbelievable and if someone had told me I would be doing that six months back I would have laughed at them.
“But the gaffer has made it clear it doesn’t matter what age you are, if he thinks you are good enough he will back you and that is fantastic.”
Saints boss Lennon once again persisted with the 3-5-2 formation that gave SPL champions Rangers a real battle before individual errors cost the Buddies after the break in that game.
At the weekend, Celts only managed to breach Saints’ defence deep into added time through Gary Hooper.
Cambuslang boy McLean says that despite the back-to-back reverses at the hands of the Old Firm, their self-belief remains undiminished.
He said: “Although we haven’t taken anything from either half of the Old Firm we have been more than competitive with them.
“The first time we played Celtic we shipped four goals so to only lose out to an injury-time goal this time shows how much we have improved.
“With Motherwell coming here next and then us going to Hamilton we have two massive tests of that coming up.
“Hopefully I have done enough to stay in for these games.”