This was a game in which they were 2-0 up at halftime against a wounded team at the bottom of the table in what was Quique Sanchez Flores' first game back in charge at Vicarage Road after replacing Javi Gracia.
Guendouzi has become a poster boy of something Arsenal have previously lacked, a bit of grit, a bit of aggression, and the young midfielder had gesticulated angrily with his teammates for not pressing with him in the first half and involved himself in some pushing and shoving with Jose Holebas as he backed Nicolas Pepe to add to that feeling.
But he was also guilty of a systemic complacency at Arsenal which was shown by the way in which they gave away both of Watford's goals. The biggest condemnation of all was that Watford racked up 31 attempts at goal — and should have won.
Arsenal head coach Unai Emery has to carry the can for the second-half performance, which was condemned as worse than that expected of "semi-professionals" by pundit Graeme Souness, and which was more damaging than the result.
"Proper teams do not play like that," Souness said, not hiding his contempt.
"They pushed us," Emery said.
In fact, they pushed Arsenal around. Arsenal appeared overwhelmed. Chance after chance was created by Watford in wave after wave of attack and Arsenal had no answer.
"We never gave up," a delighted Flores said afterwards.
Could Arsenal say the same?