Speaking to talkSPORT, Robson said he believes Ozil does not deserve a place in the team based on his recent performances, and thinks his £42.4m price tag should not merit automatic selection.
But perhaps more surprisingly, the former-Arsenal midfielder says he's heard rumours that Ozil is one of a number of German players who've become unhappy with Arsene Wenger's training methods.
"I'm not sure he [Ozil] know what his role is," Robson told talkSPORT.
"I've spoken to a few German journalists who tell me the German players aren't particularly impressed with some of the work that is being done in training and what their roles in the team are.
"Mesut Ozil is not quite sure whether he is playing behind the main striker, whether he is meant to go out into the wide left area, what his defensive duties are.
"He looks tired and, at the moment, is not worth his place in the team."
Ozil came in for criticism after another below-par performance in Arsenal's 5-1 defeat to Liverpool at Anfield on Saturday.
But he was not the only Arsenal player to struggle against Brendan Rodgers's side, as they fell 4-0 down after just 20 minutes.
But the Gunners have an excellent chance to get back on track this week, when they take on Manchester United on Wednesday night at the Emirates Stadium.
Arsenal are still well placed to mount a title challenge, and will relish the chance to play United at a time when the defending Premier League champions are struggling for form.