The Gunners boss told The Independent: "There are two things I'd like to say. Firstly, congratulations to Liverpool for winning with an emphatic score, but I think... it is a very flattering score.
"For big spells in the game, Manchester United dominated but they made mistakes on the day that usually they don't do.
"Some players looked a bit mentally tired.
"It opens up the race for the title, even though I still believe Manchester United are in a strong position with the game in hand."