The strike against United is just Mkhitaryan's third league goal of the entire season and was perfectly placed out of the reach of David de Gea.
Then came the question that must have hurt the Arsenal manager, still upset at the manner of his impending departure.
Manchester United's Marouane Fellaini was naturally pleased his last-gasp victor secured Champions League football for the Reds in a 2-1 victory over Arsenal, but insists the priority now is to continue to win in preparation for the Emirates FA Cup final.
The result seemed a foregone conclusion right from the kick-off, perhaps due to the public opinion surrounding Wenger and his trips to Old Trafford, discounting the oft-underrated fact that Arsenal had finished above Manchester United in the English Premier League for the last four consecutive seasons. However, Wenger disclosed that a meeting with the Portuguese would be unlikely.
Arsenal manager Arsene Wenger reacts during the match against Manchester United.
The Frenchman is hoping to add one final trophy to his honours list at Arsenal and his first in European competition with the Gunners playing the second leg of their Europa League semi-final against Atletico Madrid in Spain on Friday morning (Singapore time). I enjoyed it. I have come here for a long long time.
Asked about the applause he received, Wenger joked: "Once you are not a danger any more, people love you!" "I want him to stay, the club wants him to stay, I think he will stay, it is almost there", he said. "So, for him to say immediately, to change him, it is because he couldn't play".More news: Manchester City pass 100-goal mark in West Ham win
"If not in the Premier League, who knows, we still have a big match waiting for us".
From Raheem Sterling's last-gasp victor at Bournemouth in late August to City's 0-0 draw at Crystal Palace on New Year's Eve, they won 18 Premier League games in a row, demolishing the 13-match record set by Chelsea in 2016-17. There is progress at many levels but not enough to be first instead of second and not enough to win the Champions League instead of the Europa League.
So often the scene of high drama between Alex Ferguson and Wenger, Old Trafford has not been the most welcoming of venues for the 22 year Gunners boss but that didn't stop the 75,000 plus fans marking Wenger's final appearance at the ground with applause.
Romelu Lukaku suffered a foot injury against Arsenal.
"However, in the last 20 minutes we showed that we wanted to win".
Leroy Sane, Gabriel Jesus and Fernandinho scored for City, with former City player Pablo Zabaleta deflecting in an own-goal.
After beating West Ham, City are on the verge of another record.