The Hammers play host to the Hornets at the London Stadium as they look to bounce back from a disappointing 3-1 loss to Brighton last time out, as they remain firmly amid a relegation fight.
But Moyes could risk starting 36-year-old Evra just a days after the veteran left-back put pen to paper on a six-month contract with the Hammers on Wednesday afternoon, following his release by French giants Marseille.
Speaking in his column, Moyes stated that he may opt to hand Evra a start against Watford despite major backlash on social media against the signing of the former Manchester United defender.
"I’ve known Pat, I’ve worked with him at Manchester United and I know what he is capable of," Moyes said. "He has been out in Dubai with his fitness coach for the past month so he is in good condition.
"He has trained with the first team for the past couple of days and done well but there’s a big difference between training and playing a match the training we do at this time of the year isn’t at a massive level of intensity because we’re trying to save the players’ energy for the games.
"From what I’ve seen over the past day or two, I would have to say he’s not far away from playing. I’m not sure whether I would throw him in straight away but it’s something I am considering."
Evra has been drafted in after fellow countryman Arthur Masuaku remains banned for spitting and has been preferred on the left wing, leaving Aaron Cresswell as Moyes' only option at left-back.
The Hammers will be desperate to get points on the board as they sit just three points above 18th-placed Stoke City, despite sitting six places above the relegation zone in 12th.
They will also look to exact revenge on the Hertfordshire-based side, who earned a 2-0 victory over the Hammers in Moyes' first game in charge.