Antonio, West Ham's only senior striker, made a flying start to the season for the Hammers but has scored just one goal in his last eight club games.
The 31-year-old overhauled his diet and took steps to improve fitness over the summer after years of frustration and concern following a number of hamstring injuries. While Antonio has stayed off the injury list this season, he has also taken on the burden of becoming a Jamaica international, adding long trips during international breaks which have long been a concern to Moyes.
Such is Antonio's threat on the break and hold over opposing defenders when at his best, the forward transforms the way West Ham play, but the explosive striker has not looked at his most sharp in recent weeks.
The Hammers cannot drop out of the top four regardless of the result at Manchester City on Sunday, but if they are to compete for the Champions League places - or any European spot - this season, Antonio needs to be at his best for the majority of the campaign.
It is almost a year since West Ham sold their only other senior striker, Sebastien Haller, to Ajax and Moyes is yet to find a suitable replacement, increasing the burden on Antonio.
Moyes decided to leave the former Nottingham Forest man at home as West Ham travelled to Austria for Thursday night's Europa League over Rapid Vienna, hoping to have him fresh for Manchester City. Antonio should benefit from the rest, though there is a hope within the staff that it may also send a message that his recent form has not been good enough.
"He is really important to the team in the way we play," Moyes said. "He gives us a figurehead and gives the opposition different problems.
"So we need him on top form. And it's good because it's always good to have come here and not needed him. So we were able to give him a bit of a rest and hopefully, he will benefit now over the coming weeks."
It is not just Manchester City that Moyes has to bare in mind. West Ham do not have a free midweek before the New Year and face visits from Brighton and Chelsea in the week following Sunday's game at the Etihad Stadium.
A striker remains high on the shopping list in January and the Hammers are weighing up a move for 22-year-old Denmark international, Jonas Wind from FC Copenhagen, while Moyes remains keen on bringing Jesse Lingard back to the London Stadium from Manchester United following his successful loan spell last season.
Lingard is out of contact at Manchester United at the end of this season and talks over a fresh deal have collapsed, though the appointment of Ralf Rangnick at Old Trafford could change his fortunes.