The 22-year-old, who became the club's youngest ever captain last month, faces a two-game spell on the sidelines after picking up his tenth yellow card of the season away at Burnley this afternoon.
Gritty midfielder Sidwell has been a consistent performer in the centre of the park this season so will be sorely missed.
The former Brighton and Brentford loanee will also miss our league game against Plymouth Argyle in early February or, if we win our Third Round replay, our FA Cup Fourth Round fixture against either Leicester or Blackpool
But top of the Championship Ipswich will prove tough opponents for Reading next weekend so Harper and Hughes, who are likely to fill the two central midfield spots, will have to be at their best if the Royals are to pick up three precious points.
It is thought that American winger Bobby Convey will retain his place in the team for the game against the league leaders having put in some impressive performances in his last two outings.
Veteran frontman Les Ferdinand could be back from injury in time for next weekend's big game, although he will miss out on playing in Monday night's cup replay at Swansea.