The 25-year-old was not part of the squad that drew 1-1 at Griffin Park in the first visit in four days, following growing transfer speculation generated after the club rejected two bids from Brighton.
Speaking to thisiscornwall.co.uk, Tisdale said: "Ryan is unsettled at the moment, and I am just being considerate and respectful to him.
"He has had a difficult couple of weeks and I didn't feel it was appropriate for him to play on Friday night.
"He didn't train because of a hamstring injury he picked up against MK Dons, it hasn't been a good time for him.
"You have to be physically and mentally right to play a game of football."