Regular attacking-midfielder Andy Hughes missed the game due to a back injury but he should be fit to return to the side for Saturday's game against Preston.
Hughes has been in fine form this season, making him one of the first names on Alan Pardew's team sheet.
Whilst the Royals manager has hinted that both could start at Deepdale on Saturday Harper admits he would not be surprised if he is dropped.
The former Arsenal trainee told the Reading Evening Post: "If Hughesy is fit then I would bring him straight back into the side. I'm sure that's what the manager will do, and rightly so.
"I think that’s only fair. He has been excellent. There have been Premiership sides watching him.
"That means possibly taking myself out of the team as I've only played one game, but I will train even harder and try to force my way back in there."
Harps first knew he was in with a chance of playing last Thursday when he heard of Hughsey's injury.
He added: "I had a little idea last Thursday that I would be playing against because Hughesy was injured.
"I was just determined to go out there and play my normal game and I thought it worked as I felt I was the best player behind Fozzy.
"When I knew I was playing I was like a kid at Christmas. I was buzzing and really excited. I decided to approach the game like a reserve match or treat it like when you played at school in the playground.
"That is how I'm going to approach every game from now on. I will visualise it as if there is no crowd and no pressure and just get on and enjoy it."
Meanwhile, Reading's New Year's Day Clash has been brought forward from 3pm to 1pm.