The Gunners did not really get going until the 60th minute when Bukayo Saka celebrated his first England call-up with a header from Hector Bellerin's cross.
Three minutes later they doubled their lead with Nicolas Pepe's good run and finish into the bottom corner - finishing off a move with 19 passes.
They looked completely in control until David McGoldrick curled home the Blades' first league goal of the season.
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