"Strong mentality" refers to having a resilient and determined mindset. It means being mentally tough, capable of handling challenges, and maintaining a positive attitude in difficult situations. Full definition
Fans and players were screaming «animals» at us and it could break few with not as strong mentality as ours. (sbnation.com)
I liked this interview from Xhaka, you could read a sort of confidence and strong mentality in the words, he meant it. (justarsenal.com)
Well this will really show how strong the mentality of the players are and i will also like to see if Steve Bould is capable of coordinating the boys and keeping them on a winning streak through the absence of the boss (justarsenal.com)