We are defending as a group though. For the Ayew goal, there was plenty of support inside for Ivanovic to pass off Montero to, but Ivanovic showed him the outside flank and that's when it turns into a 1-on-1 game and he got beaten. Let's not act like Ivanovic isn't prone to doing this either, he's well known for struggling against quick, nippy wingers, or just 1 on 1 duels in general. He isn't great at it.