Arsenal have confirmed that new signing Henrikh Mkhitryan will wear the number 77 shirt for the club in the Europa League this season, with the Gunners set to face Swedish club Östersund over two legs in the last 32 later this month.
Mkhitaryan, who sealed his arrival as part of a swap deal with Alexis Sanchez on 22nd January, was immediately assigned the vacant number seven shirt to wear in domestic fixtures.
However, UEFA rules dictate that a player cannot wear a shirt number in a European competition that has already been worn by another player at the same club in the same European competition during that season.
As a result of Sanchez's appearance in the opening group game against Köln in September, it means that the Gunners' seven shirt is off limits in the Europe until next 2018/19.
That ensured Mkhitaryan had to choose another number for European games for the remainder of the campaign. In keeping with his usual shirt, the Armenian has chosen double seven, 77.
Arsenal would also have had to do similar for Pierre-Emerick Aubameyang, as his number 14 shirt has already been worn in the Europa League this season by the departed Theo Walcott.
However, the Gabonese international is not eligible to play in the competition at all. UEFA rules on the matter are confusing, but because he played for Borussia Dortmund in the Champions League and they are now in the Europa League with Arsenal, he cannot be registered.
Mkhitaryan can be registered because Manchester United are not in the Europa League.