Sam picked up his fifth booking of the season in the 4-4 draw with Millwall last weekend and will subsequently serve a one-match ban.
The 25-year-old's absence could see Jonjo Shelvey or Therry Racon return to the starting XI on the left flank, with Scott Wagstaff switching to the right.
Parkinson will also be without on-loan Reading striker Dave Mooney.
Mooney suffered a knee injury against Millwall, with Akpo Sodje, Leon McKenzie, Izale McLeod and Chris Dickson all vying for his place.
Meanwhile, the Addicks could welcome back Frazer Richardson at right-back after he recovered from a hamstring injury, but Kelly Youga is still out with a a knee complaint.
Swindon boss Danny Wilson will make a late check on the availability of Kevin Amankwaah.
The full-back was withdrawn just 24 minutes into last Saturday`s 2-1 triumph over Brighton with a stomach upset, but he is hoping to have fully recovered in time to line up at The Valley.
Lescinel Jean-Francois came on to replace him last week and he will again be on standby to step in, should he be required.
Otherwise, Wilson has no new injury or suspension concerns and will be reluctant to make any changes to a side that bounced back from the disappointment of their 3-0 defeat to Bristol Rovers to see off the Seagulls - their seventh victory in their last nine games.
That should mean Charlie Austin and Billy Paynter continuing their devastating partnership up front and Alan O`Brien taking his place out wide after fully recovering from hamstring troubles.
Lloyd Macklin should be on the bench again as he works on his rehabilitation from a leg fracture.
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