An impressive 2015/16 season with Benfica earned Sanches a move to the Bavarian giants where he will now team up with the experience Alonso.
Sanches gained further renown recently as he instrumental in Portugal's Euro 2016 triumph and Alonso believes that the 18-year-old will make an impact at the Allianz Arena.
"He's 18, 19 [in August], he's such a promising player," Alonso said."He has so much power, so much energy."
He's hungry to win things, to improve and I'm looking forward to working with him and to be able to share the midfield and to play together.
"So far he's European champions with Portugal.
"Can he learn from me? Maybe I'm able to learn some things from him as well."