Unai Emery said he did not hear what Troy Deeney said in his direction after being sent off in Watford's 1-0 home loss to Arsenal in the Premier League.
Moments after Ben Foster's error handed Arsenal star Pierre-Emerick Aubameyang what proved the only goal at Vicarage Road on Monday, Watford captain Deeney was dismissed.
The striker caught Lucas Torreira with his elbow as he ran past the Arsenal midfielder, referee Craig Pawson showing the red card after consulting with his assistant.
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Deeney's red card proved a key factor as Watford battled despite being down a man, with Craig Cathcart and Adam Masina both hitting the woodwork for the FA Cup finalists.