Midfielder Smith missed last Friday's win over 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 the televised showdown.
Warnock will be without Hogan Ephraim, who starts a three-match ban following his dismissal at the Madejski Stadium.
Fellow winger Wayne Routledge, who hit the winner against the Royals, should play despite needing a course of antibiotics for an abscess on his tooth.
Midfielder Akos Buzsaky played for the reserves this week after four months out with a knee injury but will not be rushed back.
Source: PA
Source: PA