In the 2010–11 season, he established himself as the starting goalkeeper for Twente. Having played in the Champions League, Mihaylov impressed with great appearances in the competition that season, among others by stopping a penalty-shot. In the Champions League FC Twente drew to play against his "nightmare" club Werder Bremen, as it were mentioned by the Bulgarian media. He only conceded one goal in the two matches played against Werder. With further appearances against Tottenham Hotspur and the previous year's Champions League winner Inter Milan in the group, Twente managed on their debut in the Champions League nevertheless to end at third place, allowing continuation in the UEFA Europa League. Twente was defeated in the quarterfinals by Villarreal, after having defeated Rubin Kazan and Zenit Saint Petersburg.