The winger pulled up with a hamstring problem during the first half of Saturday's goalless draw at the Madejski Stadium and boss Nigel Adkins is waiting to hear how serious it is.
"It's a shame we lost Hal, he's got a hamstring injury of some kind," said Adkins.
"It just underlines the demands placed upon players with games so close together.
"I don't know a prognosis at this moment, but it was a shame because he's been in good form."
Adkins did receive some positive news, though, with defender Sean Morrison is set to make his return from a knee injury this week.
Morrison, who has been out since mid-November, has been pencilled in for a behind-closed-doors friendly.