Sheffield Wednesday striker Caolan Lavery and latest signing Oguchi Onyewu are both ineligible for the FA Cup replay against Macclesfield.
Lavery, who fired an impressive double in Wednesday's 6-0 thrashing of Leeds at the weekend after returning from his loan spell at Plymouth, and USA international defender Onyewu, were not registered with the club when the two sides drew 1-1 at Moss Rose in the original tie.
Gray will recall on-loan Arsenal goalkeeper Damian Martinez in place of Chris Kirkland, while winger Jermaine Johnson and midfield pair Jeremy Helan and Stephen McPhail are pushing for recalls.
Michail Antonio, Giles Coke (both hamstring), Lewis Buxton (groin), Kamil Zayatte, Martin Taylor (both ankle) and Anthony Gardner (Achilles) all remain sidelined.
Macclesfield manager John Askey has a full squad to choose from for the cup clash with the in-form Owls.
The Silkmen came through the original tie at the Moss Rose unscathed and will head to Hillsborough fresh after a weekend off.
Askey will be tempted to stick with the same side that earned the replay with a 1-1 draw on home soil, although the likes of Paul Lewis and John Paul Kissock are pushing for recalls to the starting line-up.
Victory would see Macclesfield repeat last season's feat of reaching the fourth round, where they were beaten by eventual winners Wigan.