The former Leicester midfielder joined the likes of Alan Gow and Liam Sercombe in the treatement room when he suffered a shoulder injury in the 0-0 draw with Gillingham on March 12.
In the seven games since that match the Grecians took just four points and the most recent defeat, 1-0 to Cheltenham on Saturday, ended their play-off push despite having been in the top seven for the majority of the campaign.
The line-up that lost to the Robins was missing Kevin Amankwaah, John O'Flynn, Pat Baldwin, Mark Molesley as well as Sercombe and Oakley while a number of Grecians were playing through the pain barrier. And Tisdale admitted his side just could not cope without so many senior pros.
"It's like getting blood from a stone at times," he said. "You are trying to conjure up different situations and I would say that losing Matt Oakley in the Gillingham game was a straw too many for us.
"Of all the things you can say this year, to go into these final half a dozen games with definite starters and key players injured, was too much. We went into this game with another three missing from last week's team."
That list of absentees meant City youth products Jamie Reid, Jake Gosling, Jordan Moore-Taylor and Aaron Dawson have become regulars in recent weeks and Tisdale says even though their exposure is a positive and a sign of things to come it showed their lack of depth.
"Every side will suffer from injuries and have an injury crisis, but the difference is that, here at Exeter, there is no back up to replace them," he said.
"As much as I am very pleased with the likes of Gosling, Reid, Moore-Taylor and Dawson coming into the side and playing, if you are going to be a serious promotion-chasing team, you can't be guessing on young players.
"It is great that they have the opportunity and we will benefit from it, but we have no back-up."
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- Liam Sercombe