Aston Villa basically already managed to do that. Not that it was an unimportant game for Aston Villa, they basically managed to keep their position safe thanks to this, but at the same time, we are talking about a team that destroyed Arsenal's chance to win the league. Thanks to that game City got the advantage and even though Arsenal is still leading the league, that is only because City has one game missing and when they win that game they will get ahead for sure.
Most times, Unai Emery's tactical masterclass goes under the radar. He is a top manager and one of the best out there. He's just not consistent enough to handle a big team.
He won Arsenal home and away this season, but it was the way he approached the second leg that I found more interesting.
Aston Villa managed to keep Arsenal who are a free-scoring team from scoring any goal. What made it even more fascinating was Aston Villa scoring Arsenal two goals. A team that's set up in such a way that they don't concede so many goals.
It's one thing to score Arsenal 2 goals, it's another thing to keep a clean sheet at the Emirates against Arsenal. That's a pretty impressive work from Emery and his team.
As you said, Arsenal lost the league that day because I don't see Manchester City dropping any point from their remaining 4 games. They'll win every game they play till the end of the season.
Unai Emery is an underrated coach just as you have rightly pointed out, if no I see no reason why club like Liverpool or Manchester United won't go for him now that they are looking for good coach. The work the man has done in Aston Villa is really encouraging, he is the only one to have won Arsenal this season home and away. He has managed to keep Aston Villa in the top 4 a position Aston Villa has not occupied for many decades now. That Man would do a fine job at Manchester United compared to Eric Ten Hag. If Arsenal lose the league, it will be courtesy to Unai Emery, the day Aston Villa played Arsenal at away, it took me to the 85th minutes before I realized that Arsenal were the home side because Aston Villa played as if the Emirates stadium were there home. They were able to pocket a free scoring Arsenal and they even got a clean sheet, something Pep Guardiola and Klopp couldn't do this season.