Unai Emery said he does not know if Mesut Ozil attended Arsenal's thrilling 4-2 win over north London rivals Tottenham.
Ozil was ruled out before Sunday's clash at Emirates Stadium with an apparent back spasm.
The playmaker also missed Thursday's Europa League win over Vorskla, which came four days after Ozil was an unused substitute in the Gunners' 2-1 victory at Bournemouth.
Asked about Ozil's omission against Spurs, Emery merely replied: "He has backache."
Emery said "I don't know" when asked when Ozil had sustained the injury, while repeating the statement after being pressed on if Ozil was in attendance.
"This is a good day to speak about players who played," he added when quizzed if Ozil had been told on Saturday that he would not play.
The match itself was a Premier League classic, with Arsenal trailing at half-time when Eric Dier's goal and a Harry Kane penalty cancelled out Pierre-Emerick Aubameyang's spot-kick.
Aubameyang's stunning second levelled proceedings, before goals from Alexandre Lacazette and Lucas Torreira completed the turnaround and Jan Vertonghen was sent off late on to compound Spurs' misery.
Next up for Arsenal is a trip to face Manchester United on Wednesday, with their last league win at Old Trafford coming in September 2006.
And Emery is excited by the challenge.
"We know it’s very difficult in Manchester - in history and in the present," he added.
"We want to prepare in the best possible way to have the best performance. This is a big challenge for us and we want to have challenges like Wednesday."
