Sanchez promised the striker that he would give him the captain's armband when they play in the Champions League after he grabbed an injury-time winner against Real Betis in March.
Girona, who had never qualified for Europe's top club competition in their 94-year history, finally secured a place in the Champions League by finishing third in the LaLiga standings last season.
"Stuani deserves to be in the starting eleven. He has been wearing this shirt for many years. He deserves it more than anyone," Sanchez told reporters on Tuesday.
"The reality is that last year we did things spectacularly. We have arrived at a place that we deserve. We are excited, motivated.
"It's a dream and you have to enjoy it. The growth of this club is demonstrated by moments like this. We have to give our version and enjoy ourselves."
Uruguay international Stuani said it was a dream come true to play in the Champions League with the club he joined in 2017.
"It is a pride and an honour to be part of all this. It's very special. Not only because of what it means for Girona to play in the Champions League," Stuani said.
"I'm lucky and it's a privilege to be able to enjoy a game like this. It's a dream day and I'm going to achieve it with the club of my life."
