Pellegrino calls for VAR after controversial Doucoure equaliser
The Saints looked to be marching towards a 2-1 win at Vicarage Road until Doucare popped up in stoppage time to rescue a point, but replays showed he had beaten Alex McCarthy with the use of his hand.
It was missed by referee Roger East, though, and the goal stood to see Watford complete a dramatic comeback, the Hornets having been 2-0 down at half-time.
Southampton have now not won in 10 league matches – a run that stretches back to late November – and they find themselves one point above the bottom three.
Despite the clear frustration within the visiting ranks, Pellegrino was not keen to dwell on the contentious end to Saturday's encounter that would not have stood with VAR.
"For sure [we should have won] but football is like this sometimes, small details change everything," he told BBC Sport. "We are very sad but we have to accept the rules. It's part of football.
"I never see this type of mistake in the Premier League before. To live [with] this injustice is really hard.
"I think we have to try [VAR] and analyse if it's possible to help the sport to make better decisions, even for the referee."
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Marco Silva was less inclined to discuss his side's equaliser, suggesting it was about time a decision went Watford's way this season.
"I don't need to talk about the [Doucoure] goal," he said. "Something can happen and this season we've had decisions go against us.
"I understand Southampton are unhappy like I was not one time, more than one time when the mistake is against us. It can happen."
Striker Troy Deeney was more willing to address the nature of their leveller, admitting it would have been disallowed were VAR part of the Premier League.
Speaking to Sky Sports, he said: "It's one of them. They'll feel like it's a loss. VAR comes in we probably wouldn't get that but we got it.
"It's the luck of the draw."