The German was substituted after being booked against Borussia Dortmund in midweek, when the Gunners lost 2-0 to Jurgen Klopp's side in the Champions League.
And former Liverpool and Nottingham Forest striker Collymore feels Ozil has become a liability for Arsene Wenger's men.
Indeed, Collymore believes Ozil is no longer worth his place in the Arsenal side.
"Mesut Ozil was supposed to make the difference for Arsenal but he was booked and got substituted against Borussia Dortmund. He's ended up being a liability for them," he wrote in his Bleacher Report column.
"Real Madrid aren't daft. They let Ozil go for a reason and he's now not worth his place in the Arsenal starting XI.
"Yet Arsene Wenger continues to pick him, as you feel obliged to whenever you spend that kind of money on a player."
Collymore is far from the first pundit to criticise Ozil since he joined the north London side for £42.4 million in 2013.
Many have leapt to the 25-year-old's defence, however, suggesting the subtle nuances to his game are not appreciated by his critics.
It seems the debate will rage on.