Clarke has missed City's last two games with a calf complaint while Dieng was sidelined for Tuesday's win over Northampton Town after picking up a knee problem.
City assistant manager Kenny Black says the duo have both been making progress recently at the training ground and either one, or both, could still feature at the County Ground.
Black said: "Every day they are both getting better, so we are hopeful for the weekend.
"Both players have been a big miss for us.
"Billy and Timothee have made a number of contributions for us so far this season and it'll be fingers crossed that we can have them available for Saturday.
"They will certainly give us greater options if they are both fit to play."
Tony McMahon made a welcome return to action on Wednesday, playing the first half of City's reserves win over Rotherham United on Wednesday.
Black added: "He is not far aware now.
"He will be another welcome addition to the squad. It will be nice to welcome him back into an already strong squad of players."