Masuaku returned to action after a six-match suspension in Wednesday's 3-1 friendly victory at Dagenham & Redbridge, while Fernandes is fit again after recovering from three-and-a-half months out with an ankle injury.
Both players have now gone off on international duty - Masuaku with DR Congo for a friendly in Tanzania and Fernandes with Switzerland U21s, who face a vital UEFA European Championship qualifier against Portugal in Neuchatel - and Moyes hopes both will return unscathed and be available for selection against Southampton on 31 March.
"We hope [to have a stronger squad for the Southampton game]," said the manager. "We've not necessarily got loads of players back, but we've got Arthur back from a long suspension and Edi Fernandes has been taken away by Switzerland to play, I hope, because he would have got a bit of time against Dagenham, but we're not getting a chance to see him [in person].
"Hopefully those two will add to the squad in the coming weeks but, other than that, I think most people are aware that we've got some quite long-term injuries."
Masuaku, who will make his DR Congo debut in Dar es Salaam, and Fernandes are just two of more than 20 West Ham players who have been called-up by their countries at both senior and age-group level.
Manuel Lanzini (Argentina), Marko Arnautovic (Austria), Joe Hart (England), Angelo Ogbonna (Italy), Chicharito (Mexico), Sead Haksabanovic (Montenegro), Joao Mario (Portugal), Declan Rice (Republic of Ireland) and Cheikhou Kouyate (Senegal) have also jetted off for a selection of friendly matches across the globe.
And manager Moyes believes endorsement at international level can only boost the confidence of his players ahead of the Premier League run-in.
"I think it's good [they've been called-up]. I think the more international players you've got at your club, it says a lot about your club, even though it gives you a smaller training group.
"We've got players away and we're roughly training with eight or nine now, so we don't carry a massive squad and having those players taken away from us now leaves us quite light.
"But the more international players you've got, the better, and that's the way I look at it."