The culmination of Liam Ridgewell's return to the Portland Timbers following his loan spell and Leon Barnett's injury will likely see Jason Pearce make his first appearance for the club.
The defender joined the Latics during the January transfer window from Leeds United and has yet to feature for the first team.
Speaking about team news for the Reading game, Mackay said: “We’ve had a couple of issues in terms of small injuries. Leon Barnett has a problem which will probably see him out of the game.
“That allows for others to have a chance, especially with Liam Ridgewell’s loan ending last week.
“We’ve got the option of bringing in the former captain of Leeds United in Jason Pearce, so we’ve got a more than good enough replacement. Jason has been working extremely hard since he arrived. He’s been patient and now is the time for him to step up for us."
There is also another battle for the other centre back spot between new loanee Harry Maguire and fans' favourite Emmerson Boyce.
“Chris McCann will still be out for this one, he’s probably a week or 10 days away after tweaking his hamstring, and obviously Emyr Huws and Grant Holt remain long term absentees.”