Monaco defeated Barcelona 2-1 in their Champions League opener, capitalizing on an early red card for Eric Garcia and securing the win with a late goal from George Ilenikhena despite a stunning equalizer from 17-year-old Lamine Yamal. In Italy, Arsenal managed a goalless draw against Atalanta, thanks to a remarkable double-save by goalkeeper David Raya. Atletico Madrid secured a dramatic 2-1 win over RB Leipzig with a last-minute header from Jose Maria Gimenez. Bayer Leverkusen had a strong start, thrashing Feyenoord 4-0 with a brace from Florian Wirtz and an own goal by Timon Wellenreuther. Benfica also won narrowly, beating Crvena Zvezda 2-1 in a hard-fought match.