Moussa Dembele admitted to being "sad" about starting on the bench before producing his heroics for Lyon against Manchester City.
Dembele was introduced in the second half and struck twice in a 3-1 win in the Champions League quarter-finals on Saturday.
Kevin De Bruyne had earlier cancelled out Maxwel Cornet's opener before Dembele helped deliver Lyon's surprise victory.
The 24-year-old said he was upset about not getting a start and joked on social about how many goals he could've scored had he played the full 90 minutes.
"Of course, a player is always sad when he doesn't start a game," Dembele said.
"But it's important to stay focused because a match is long. As long as the referee hasn't blown the whistle, it's not over.
"When I came into the pitch, I did everything I could to help the team win."
— Moussa Dembélé (@MDembele_10) August 15, 2020
Lyon's shock win sent them into a semi-final against Bundesliga champions Bayern Munich on Wednesday.
Dembele believes Lyon, who finished seventh in Ligue 1, have been a different side since returning from the coronavirus-enforced break last month.
"After the break, we promised ourselves that we would give everything. Every time we are on the pitch, we try to give 100 per cent," he said.
"I think the spirit of the group has changed and that's good for the future. We're still in this competition so that means we're a great team."
Dembele began his senior career in the Premier League with Fulham before joining Scottish champions Celtic in 2016.
The now 24-year-old linked up with Lyon in 2018 and has scored 24 goals in all competitions for the club this season.
Lyon manager Rudi Garcia was happy to see Dembele make the most of his limited minutes on Saturday.
"Moussa was disappointed but as I said before the match, I knew he was going to be decisive when he came on," Garcia said.
"I am delighted that he scored twice as he had not yet scored in the competition."
Dembele has now scored four goals against Manchester City in the Champions League - the joint-most against the club in the competition since Guardiola took over in 2016.