Chelsea forked out a British transfer record £107m to sign Fernandez from Benfica on winter transfer deadline day.
The 22-year-old Argentine won the FIFA World Cup back in December and was named young player of the tournament.
Rice is a full England international but the 24-year-old has only 18 months left on his contract with the Hammers.
Reports suggest Rice has turned down several approaches by West Ham to extend his contract, leading to links with the likes of Arsenal, Newcastle United, Chelsea and Manchester United.
After watching Rice put up another impressive display in a 1-1 draw against Newcastle United on Saturday, Moyes has tipped West Ham's captain to command a British record transfer fee if he does leave the London Stadium.
Hammers boss Moyes said: “I don’t know if I need to say the words, I think you can say the words if you watched it the way I saw it. I thought he was a top player in the first half, he really was, he showed so many things.
“Undoubtedly Declan is going to be a top player. Undoubtedly he’ll be a British transfer record if he ever leaves West Ham.”
Asked if Rice’s departure was inevitable, Moyes said: “I hope it’s not, I hope he sees his time here.
“But look, there’s a lot of talk about it and when you see what’s going about for the prices, I think Dec will be blowing that (British record) out of the water, that’s for sure, when it comes around.”
