The Reds take on Villarreal at Gdansk Stadium with the chance to claim a first piece of silverware under Ole Gunnar Solskjaer.
McTominay says building momentum and experiencing that trophy-winning feeling is vital for the team and he insists the players know they must take this chance.
“[It's the] spiral effect. It's that experience of knowing we can win, building winners within a team, that winning mentality can't just be brought to us afterwards if we win a trophy,” he explained.
“It has to be there instilled in the players before that, it has to be us going to the final knowing we're going to win, pushing for that trophy.