The Brazilian spent last season on loan at Granada, and although they were relegated, he was one of the few players to come away with any credit.
And after a season of “men's football", he feels capable of impressing Jose Mourinho at Old Trafford.
He said: “I think I'm ready now. I have played over 2,000 minutes now in men's football, in La Liga, and I did quite well. I feel I'm ready, more than ready, to play men's football now.
“I am more mature as well, physically and mentally, and I am ready to come back and hopefully push to play next season for United."