Already in the 14th minute, Guirassy scored a shot just inside the left post, which he followed up with another goal ten minutes later. Both times after an assist by Karim Adeyemi.
The 29-year-old Guirassy, who was born in France and plays for Guinea's national team, has now scored three goals in four matches in the tournament.
I think I could have scored at least three goals, but I'm glad I could help the team win, he says to the TV channel DAZN after the match.
In the second half, the match turned and Monterrey dominated. But despite the Mexican team having several chances to equalize, with an advantage in both ball possession and shots on goal, the Germans held out and won 2-1.
The win means that Dortmund will now face Real Madrid - who won 1-0 in an afternoon match against Juventus - in the quarterfinals on Saturday.
I expect a very tough match. Real Madrid will want to advance so it will be tough, but we will be prepared, says Guirassy.
Dortmund's Jobe Bellingham received a yellow card in the 28th minute and will therefore miss the match against Real - and the chance to play against his brother Jude Bellingham - due to too many yellow cards.
