The influential midfielder limped out during the first half of Tuesday night's 2-2 draw against MK Dons with a dead leg.
With Adam Chambers still missing with a hamstring problem, Os boss Russell Slade will be desperate to get Dawson fit in time to travel to south Wales.
Full-back Elliot Omozusi has been sidelined since suffering a hamstring injury in the third-round win at Norwich and remains doubtful, with Andrew Whing likely to deputise again.
Tottenham youngster Tommy Carroll has joined until the end of the season and is eligible along with fellow Spurs loanees Harry Kane and Paul-Jose Mpoku.
Defender Aaron Brown this week joined Stockport on a month's loan.
Source: PA
Source: PA