Midfielder Smith missed Friday's win at Reading with a hamstring problem and striker Helguson has been struggling with a groin injury.
But manager Neil Warnock expects the key duo to be fit in time for Sunday's televised clash.
Warnock will be without Hogan Ephraim, however, after the winger was hit with a three-match ban for his dismissal at the Madejski Stadium.
Ephraim saw red for sliding in on Jimmy Kebe but Warnock said: "I was a bit disappointed with the sending-off, it was a bad tackle but one that involved two wingers."
Source: PA
Source: PA