The midfielder believes that the Arsenal man is to blame for Manchester City's second on Sunday.
Arsenal travelled to the Etihad Stadium over the weekend looking to bounce back from their midweek loss to Everton.
They were unable to do so, though, as goals from Leroy Sane and Raheem Sterling handed Pep Guardiola’s team all three points.
The Gunners were heavily criticised for the defeat after putting in a lacklustre second-half showing.
The likes of Mesut Ozil have been particularly singled out but Adam put his attention on someone else in the Arsenal team.
"Nacho Monreal has to do better [for the second goal],” he told Match of the Day 2.
“Monreal backs off and allows Sterling in the box - and as soon as you allow someone like Raheem in the box you've got a chance. It's a goal - it's not offside."
It will be interesting to see how Arsenal react to their back-to-back defeats as they attempt to keep their title hopes alive.
They have West Bromwich Albion and Crystal Palace at home in their next two games and will be expected to come away from those with maximum points.
Should they fail to do so, it is easy to imagine that Arsenal's title challenge will be over given they are already nine points behind leaders Chelsea at this stage.