King joined Boro on loan from Millwall on Thursday and is eligible to feature against the Royals at Broadhall Way
Midfielder Terence Vancooten remains a doubt after suffering a facial injury on Boxing Day which has kept him out of the last two games.
Forwards Alex Samuel and Jamie Gray and midfielder Dale Gorman are among the players pushing for starts, although manager Darren Sarll could name an unchanged line-up following the 4-1 victory over Cheltenham on Monday.
Under-fire Reading manager Jaap Stam will freshen up his side for their trip to Hertfordshire.
Tiago Ilori, George Evans, Omar Richards and Jon Dadi Bodvarsson are all likely to feature for the Royals, who have slipped to 18th in the Championship.
Forward Joseph Mendes and midfielder Stephen Quinn (both knee) are also still in rehabilitation.
Defender Jordan Obita is out for the season after surgery on his anterior cruciate ligament.
Burton midfielder Martin Samuelsen will use the international break to recover from illness after pulling out of Norway U21's games.
Jonas Lossl is staying 'optimistic' over Huddersfield's chances of survival this season and has urged his team-mates to 'go for it'.