The Gunners entered the Premier League clash in good form after Arsene Wenger’s side were 5-0 winners against Southampton in the FA Cup fourth round on Saturday evening.
However, Watford eased into a commanding first-half lead thanks to goals from Tottenham defender Younes Kaboul and Troy Deeney in the opening 12 minutes at The Emirates.
Arsenal managed to halve the deficit in the second half through Alex Iwobi before Spanish striker Lucas Perez hit the woodwork but the Hornets clung on for three points.
Chelsea, meanwhile, played out a 1-1 draw with Liverpool after Georginio Wijnaldum cancelled out David Luiz’s opener but the Blues still managed to extend their lead to Arsenal to nine points after the result at The Emirates.
Speaking to Arsenal’s website about the north London side’s setback in the title race, Cech said:
“I always say that at this level you cannot play 80 minutes, or 85. You have to play 90 minutes with full concentration and everybody on top of their game.
“It was too much for us to take in the first half and it’s very hard to say why because we were prepared, we were on back-to-back wins, important wins, we had the momentum after the Burnley game and obviously the Southampton game went completely our way, exactly the way we wanted.
“This was a huge setback because this was the game we wanted to win and we wanted to put ourselves in a better position going into the weekend.”
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