Fortune's contract expires this summer and although the 31-year-old will miss the next three games after a red card last weekend, Clarke said that will have no bearing on his thinking.
"He's got a chance of playing again this season because his suspension will be three games," he told the Express and Star.
"He is one of a number of players that we'll need a decision on his contract.
"I said a few weeks' ago that what happened between now and the end of the season wouldn't have any bearing on the decisions that I make.
"I'll sit down with Richard Garlick (sporting and technical director) and the chairman in the weeks coming up and we'll decide how we're going to shape the squad."