The Gunners are unbeaten since their loss to Liverpool at the end of August, but going into the game against the Hornets, they could be without two of their key defenders in Shkodran Mustafi and Laurent Koscielny.
The former suffered a muscle injury during Germany's 5-1 win over Azerbaijan and manager Joachim Low's assessment suggested that Mustafi could be facing a long spell on the sidelines with a possible ligament tear.
The 25-year-old defender's injury is still being assessed and the true extent is likely to be revealed during Arsene Wenger's pre-match press conference on Thursday (12 October).
Koscielny, on the other hand, skipped the recent international break to recover from an Achilles injury that has been a long-standing issue for the France defender. He missed Arsenal's game against Brighton, and according to The Telegraph, he is yet to return to full training and could miss the trip to Vicarage Road as well.
If both defenders are unavailable, Wenger will have to turn to back-up options Per Mertesacker and Rob Holding to fill the void, as Calum Chambers also remains sidelined with a hip injury.
Meanwhile, according to the Mirror, Mesut Ozil, Francis Coquelin and Danny Welbeck are closer to making their returns, but the Arsenal manager could be wary about rushing them into action too soon. The manager expects the trio to return to training ahead of the game against Marco Silva's side on Saturday.
The only long-term absentee is Santi Cazorla, who has not played since October 2016. The Spanish midfielder has just begun his recovery process from multiple surgeries to his Achilles, but is not expected back before Christmas.