The Mexico striker has missed West Ham's last four games with a hamstring injury but his return to the fold comes at an ideal time for the Hammers.
Moyes's side, who have lost three and drawn one since Hernandez has been missing, posted a hugely encouraging performance in Sunday's 2-1 defeat at Manchester City, coming within minutes of doing what only one other team has done this season and make the Premier League leaders drop points.
A loss, but a very spirited loss nevertheless and Hernandez's return should raise hopes ever so slightly that they build on that performance and take something off Chelsea.
The former Manchester United marksman has scored four in 11 Premier League games since joining in the summer and the Irons have only managed two goals in his absence - one from Cheikhou Kouyate, a centre-midfielder, and another from centre-back Angelo Ogbonna.
Another subplot for West Ham at the weekend comes between the posts and Moyes is expected to keep faith in Adrian after an outstanding performance at the Etihad in place of the ineligible Joe Hart, who is on loan from Pep Guardiola's side.
But there were no clues in training as to who would get the nod, with both goalkeepers involved.