Arteta elaborated on the situation during his post-match interview, explaining the visible symptoms that made it clear Havertz could not participate.
"With Kai it was obvious [that he could not play against Brentford]. He wasn’t feeling well at all and he had very clear symptoms. So stay away from it, put him in a car, and go back to London," he told reporters.
"These things happen. In this period, there are always things - throat, infections, viruses. So I try to delay the lineup as well, as far as possible, because you can get up in the morning and you can have a surprise unfortunately.”
However, Arteta expressed optimism about his recovery before the fixture against Brighton and said: "I think so, yeah. Hopefully he will recover very quickly."