Wenger took his Gunners side to Germany tonight to face Pep Guardiola's Bayern in the second leg of their Champions League tie, trailing 2-0 from the first leg.
But there was confusion from the off as many Arsenal fans and football supporters in general noticed something perplexing - Arsenal named just six substitutes out of a possible seven.
The news finally filtered out that Arsenal had made a bizarre error - they forgot that Japanese youngster Miyaichi was unable to play in the Champions League.
The 21-year-old was supposed to be on the Gunners bench for tonight's game at the Allianz Arena, until the club realised that he was ineligible to play. Miyaichi was registered on the 'B' list, but a UEFA ruling states that in order to qualify for that list, a player would have to have played for their team continuously for three years.
But having featured for Feyenoord and Wigan Athletic on loan deals, Miyaichi was subsequently unable to take his place on the bench, leaving Wenger one man short of his full substitute options.
Kieran Gibbs and Yaya Sanogo didn't make the flight to Germany, but in the end it didn't really matter, as Arsenal could only muster a 1-1 draw in Bavaria, meaning they crash out of the competition in the first knockout round - much to the disappointment of the Arsenal fanbase.