Chelsea manager Thomas Tuchel and Southampton counterpart Ralph Hasenhuttl bemoaned key video assistant referee interventions after the Blues won 3-1 against their 10-man opponents at Stamford Bridge.
Chelsea forward Timo Werner had a first-half header ruled out because of a foul in the build-up by Cesar Azpilicueta, while Saints had captain James Ward-Prowse sent off for a late challenge on Jorginho with the score at 1-1.
Both decisions were made after input from VAR Mike Dean - Werner's goal had been awarded by on-field official Martin Atkinson, who later chose only to book Ward-Prowse for his sliding tackle.
Hasenhuttl said he felt "relatively clear" Ward-Prowse would be sent off once Dean had instructed Atkinson to review the midfielder's challenge.
"It's always a little bit of a problem when we know Mike Dean is VAR because we have not had a good history with him to be honest," Hasenhuttl told BBC Radio 5 Live.
Speaking to BBC Match of the Day, the Saints boss added: "When you press high then you sometimes have situations like this when you are a bit late.
"[On] the red card from VAR Mike Dean, it is the third time he gave us a red card while I am here, but OK."
Ward-Prowse had drawn the visitors level from the penalty spot after 61 minutes, cancelling out Trevoh Chalobah's opener.
But winless Southampton could not hold out for a point following Ward-Prowse's dismissal with 13 minutes remaining, as Werner and Ben Chilwell struck in the final six minutes to send Chelsea top of the table.
Chelsea 3-1 Southampton: Thomas Tuchel bemused by VAR decisionTuchel was relieved with the result but said he "could never believe" the decision to disallow Werner's first-half goal.
Azpilicueta was adjudged to have fouled Kyle Walker-Peters in regaining possession on the right before crossing into the box. Though Romelu Lukaku was unable to reach the initial ball, Werner found the net when Callum Hudson-Odoi sent it back in from the opposite side.
Atkinson viewed the pitchside monitor and Tuchel received a booking for his reaction to the resulting decision.
"I was very angry because I could never believe this could happen in the Premier League where you would go back to a 50-50 that wasn't even in close connection to the goal," Tuchel said.
"I understood before the season that we didn't want soft touches, that we wanted a contact game.
"We are here today in the middle of London in the rain in an intense game but the ref disallowed the goal."
