Following his world-record transfer from Tottenham, the Wales international is expected to be involved for Carlo Ancelotti's side, having featured for his country against Serbia on Tuesday.
The 24-year-old could even line-up at full back after Marcelo and Fabio Coentrao both suffered injuries during the international break.
"We have to wait until the match day to see whether I'm picked or not," he said. "But hopefully I can get my fitness up straight away and get a place in the team.
"I have spoken to the boss about where I'm best on the pitch but I will play anywhere I'm asked."
"It's a chance to show that we can compete with anyone and that we can fight against a team like Madrid," he said.
"Last year, we were dreaming about playing these teams and now the opportunity has arrived and we want to put in a great performance.
"Personally I prefer it if an opponent is at full strength and that the best come so we can take them on.
"Although even if Madrid has some players out, I am sure they will have the same level of quality."
Bojan Jokic (hamstring) and Francisco Farinos (Achilles) are doubts for the hosts having already missed the opening matches of the season.
