The Grecians beat Walsall 4-2 on Saturday to avoid the drop for another week, but still sit five points from safety with two games left of the campaign.
The Devon club must win their remaining fixtures, and hope results elsewhere go in their favour, to complete an extraordinary survival mission, but Tisdale has not ruled out such a scenario just yet.
He told BBC Devon: "We all know that it's going to be highly unlikely, but until it's over it's never over. The way we've played in the last three games at home and the way we played away at Scunthorpe and Rochdale, you never know.
"We're putting form together now that I'd have hoped we'd have produced earlier.
"It may be a bit late but better late than never, and if we're going to lose games let's lose them playing well and it'll give us a moral boost going into next season."