The Portuguese manager was sacked by Sheffield Wednesday on the eve of Christmas but was surprisingly employed by the Welsh side two days later.
Andre Carrillo gave Watford the lead in first-half but Ayew brought Swansea level after the break before Luciano Narsingh got the match winner three moments later.
“He was vocal because we were not winning enough duels and we were not aggressive enough in the first-half," Ayew was quoted as saying by Daily Star.
“He told us to win our duels first and then play our football. In the second half that’s what we did and he got what we wanted,” he added.
Watford midfielder Ben Watson believes they didn't kill the game off and allowed Ayew enough spaces to find the equaliser but hopes they will improve against leaders Manchester City.
“I don’t know how we lost it. We were in control of the game but didn’t kill the game off and got punished by Ayew,” he said.
“It’s not the first time this season we have paid the price. If you don’t finish teams off they are always in the game.
“We will go over things and we are gutted. But that’s the Premier League and we have to bounce back. We will learn from it and learn from this quickly,” he added.
Although, Swansea are still at the foot on the log, they are now tied on 16 points with West Bromwich Albion and only three points below safety as they welcome Tottenham Hotspur on January 2.