Vidot did not feature in the win over the Giants and was not named in the Red Devils 19-man squad.
The 26-year old has only made six Super League appearances this year after overcoming an injury at the start of the season.
Vidot’s last match came against Huddersfield on June 17.
Watson said the Samoan international was available for selection for Sunday’s game but was overlooked.
“He’s available for selection,” Watson said.
“He’ll tell you his performances weren’t up to what his standard should be.
“We’ve had some chats, between myself and Vidot, and he knows, he’ll put his hand up and say he hasn’t been playing his best rugby.”
Forward Josh Jones also did not play on the weekend after beng selected in the 19-man squad.
“There’s just a couple of issues with Josh,” Watson said.
“He was a late replacement. Josh is just dealing with a few things at the moment. It’s something every club has issues to deal with.”