Manchester United are facing an injury crisis in their backline for their match with the Gunners.
Eric Bailly has a back problem, Luke Shaw and Antonio Valencia have knocks and Ashley Young is suspended.
Marcos Rojo could feature as the Argentine hopes to play his first competitive match since the World Cup.
Smalling has been told to rest and will be evaluated as close to kick-off as possible.
Mourinho was forced into playing Scott McTominay and Nemanja Matic in central defence in the 2-2 draw with Southampton on Saturday.
Man Utd boss Jose Mourinho is desperate for a win against Arsenal (Image: GETTY)
Man Utd news: Chris Smalling is an injury doubt for the match against Arsenal (Image: GETTY)
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After the match the Portuguese said: “I think Scott [McTominay] and [Nemanja] Matic did a very positive job for two midfield players and Phil Jones led that group of three in a way where we were totally in control.
“I would say that the only problem that we had was that the two attacking players didn't have enough continuity, because in midfield we lost too many balls.”
Mourinho did accept it was two points dropped though against the side who have now sacked Mark Hughes.
He explained: “Yes [it was two points dropped]. The result is not good so I have to say we dropped two points.
“If you are losing 4-0 and you get to 4-4 I would say maybe not.
Man Utd striker Marcus Rashford limped off against Southampton (Image: GETTY)
“I think the comeback is good from 2-0 down to 2-2 in normal conditions everybody says it is a point gained, you have the game lost and you get a point, so normally you say it is a positive point, but it is a match that we want to win.
“It is a match where because of that good reaction in the first half we had 45 minutes to win the game. It was not like we had 10 minutes to win it, we had 45 minutes, so for me obviously it was not a good result.”
United will be desperate to pick up a big win against Arsenal tomorrow.
The Gunners have momentum though after beating rivals Tottenham 4-2 at the Emirates on Sunday.