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Arsenal had bad record when facing Bayern Munich in last several matches before on Champion League, season 2016/17 its the last time participating by Arsenal and defeating many goals by Bayern on first and second leg matches when Mikel Arteta still as players. Currently its not matter with how many matches Bayern Munich leaded head to head, both teams performance in Champion League and domestic league this season drastically difference, Arsenal had better performance lead the top position in domestic league and Bayern Munich loss their performance and this season seems can't be the Bundesliga winner.
Arsenal this time has chance for eliminating Bayern Munich in quarter final round, not matter with how many matches Bayern Munich lead head to head but Arsenal currently has better performance than Bayern.
I think the difference in performance between the two teams in the domestic league will not be a complete benchmark for what their chances are in the Champions League match. The atmosphere of the Champions League is very different compared to the domestic league, so it is always difficult to predict the result of the match even though the two have a previous meeting record.
Arsenal is not worse than Bayern Munich, but Munich is also not better. I think both will try to beat each other at their respective home courts where each home team is favored to win. Arsenal have been good under Mikel Arteta, but I wouldn't say Tuchel has been bad for Bayern Munich so far.