The utility player returned to pre-season training after suffering the injury while out for a run on his own during the summer and it was feared he would be forced to sit out most of the preparations.
But Stimson said: "It's not as bad as we first thought so that's good. He can start to up his workload now. I don't know if anyone's seen him but he's brought his own bike in from home and been cycling around everywhere to try and keep his fitness up.
"He's had to stop training with the boys and the football but he can cycle so he can keep his endurance work going up to a point. We'll see how he goes, it's just a matter of not overdoing it and not getting a reaction.
"If we can go along then touch wood in a week's time he'll be able to join in the warm-up and we'll go from there."
The Gills start their pre-season campaign on Saturday at local non-league side Folkestone Invicta and will include four trialists in the shape of former Crewe defender Chris McCready, ex-Yeovil centre-back Aaron Brown and former Charlton duo Sam Long and Rashid Yussuff.