Watford boss Marco Silva is set to name Gray in his starting XI just days after he completed his £18.5million switch from Burnley.
He is likely to play up top on his own, with club captain Troy Deeney still struggling with a groin injury.
Deeney had surgery a month ago and he now faces a late fitness test before kick-off on Saturday.
Defender Craig Cathcart misses out with a groin injury and he is joined on the sidelines by Christian Kabasele and Mauro Zarate.
Team from: Gomes, Pantilimon, Janmaat, Britos, Kaboul, Prodl, Mariappa, Holebas, Femenia, Hoban, Capoue, Hughes, Amrabat, Chalobah, Behrami, Doucoure, Watson, Pereyra, Deeney, Success, Richarlison, Sinclair, Okaka, Gray.