Mkhitaryan joined Arsenal as part of the swap deal which took Alexis Sanchez to Manchester United in January.
And the Armenian has made a bright start to life at the Emirates with four assists in as many games so far.
Mkhitaryan is cup tied for Sunday’s Carabao Cup final and will therefore be used by Arsenal manager Arsene Wenger tonight.
But the 29-year-old, who was given the number seven shirt when he signed, will have the number 77 on his back.
UEFA regulations state two players cannot wear the same shirt number in the same European competition.
Earlier this season, Sanchez wore the number seven shirt in the Europea League and it means Mkhitaryan is not allowed to wear the same number despite him sporting it in the Premier League.
Arsenal go into the second leg with a 3-0 advantage which was established last week.
With the Gunners currently sixth in the Premier League, their best chance of Champions League qualification could come through winning the Europa League.
But Mkhitaryan believes Arsenal are still capable of securing a top-four finish.
He told ESPN: “Of course, it [Europa League] is very important, but I wouldn’t say we stop ourselves from saying we are going to compete in the top four.
“We are still in the competition because in the English Premier League anything is possible.
“Maybe sometimes, teams can lose two, three times in a row and we win our games so anything is possible.
“We are trying to win every game in every competition and, of course, we will be glad if we can win the Europa League as well, but if we can be in the top four, it will be even better.”
