The Germany global was one of seven senior players to miss training on Wednesday and was not part of Arsenal's matchday squad for the 3-1 victory over Koln in the Europa League on Thursday evening.
Despite the initial hiccup, Ozil will always be a vital component in Wenger's first-team plans at the Emirates since his creativity and vision continues to be unparalleled.
"But our record against Chelsea recently has been good".
Arsenal failed to finish in the top four of the English Premier League last season hence missing out on a place in this season's UEFA Champions League.
However, it is not immediately clear where Ozil would fit in Mourinho's current attack at Old Trafford, especially as the German has endured mixed fortunes in the Premier League since moving to Arsenal in 2013.
Arsenal will compete in the Europa League where they are in Group H with FC Cologne, Bate Borisov and Red Star Belgrade.
Wenger is unsure if the Alexis Sanchez will start at Chelsea despite being confident that three days is sufficient for the players to recover. "It doesn't bother me".
Merson has been a vocal critic of Arsene Wenger for some time and the Sky Sports pundit has now used his weekly assignment of choosing a combined XI of the two teams taking part in the game of the weekend.to criticise Wenger's side again.
"The contract talks [with Mesut Ozil] have slowed down a little bit since August 31, because we need a little breather and to focus on the competition", said Wenger. The French centre back has been widely accepted to be one of the best in the EPL for the last few years, but Merson reckons that it is actually the aging and slow Per Mertesacker who is our best defender.