Mikel Arteta was seen 'screaming' at Kieran Tierney before his confrontation with Cucho Hernandez.
It was a difficult afternoon at the office for the Gunners despite securing a 3-2 win at Vicarage Road as the likes of Emmanuel Dennis and Hernandez caused their defence all sorts of problems.
The Colombian, who scored an acrobatic finish to cancel out Martin Odegaard's opener, imposed himself down the right-hand side throughout the 90 minutes.
Tierney was given the task of containing Hernandez and he had his hands full as the former Celtic star failed to deal with the tricky playmaker.
Arteta wasn't best pleased with how Watford were able to find so much success down that side and was seen yelling at Tierney and Gabriel Martinelli for neglecting their defensive assignments.
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The Spaniard screamed at Tierney for not getting out to Hernandez quick enough at one point in the first half, before reeling away to complain to the officials after Martinelli failed to provide cover for the Scottish left-back.
Tierney's dual with Hernandez came to a head in stoppage time as the Arsenal man seemingly offered to meet the Watford player after the full-time whistle.
Watford made a late surge for an equaliser after Moussa Sissoko's 87th minute strike but Arsenal were successfully able to wind the clock down.
Roy Hodgson's men construed it as time-wasting, however, as tempers flared between both sets of players.
Tierney was taking his time to take a throw-in which Hernandez took exception to as he put the ball in the defender's hands in an attempt to get play restarted quickly.
Tierney exaggerated the contact, falling to the ground briefly, which prompted an angry reaction from Hernandez who believed he was play-acting.
Tierney got back up and signalled to Hernandez that he would meet him after the game to settle their differences.
Hernandez walked away from Tierney, as a result, as play resumed with Arsenal seeing out the victory.
Arteta was animated on the touchline and he couldn't hide his disappointment with Arsenal's overall display at his post-match press conference.
"We were really good going forward and we had all the right intention and the energy to do it," he said. "We scored three magnificent goals but we didn’t have the same energy and commitment defensively.
"When that happens, to win a game from home, you’re going to suffer. That’s why we suffered today - because defensively we didn’t have the right structure. We didn’t detect with enough urgency the moments where they could activate certain spaces that we knew.
"That’s why we suffered. We conceded two and we could have conceded another one or two."
