The 25-year-old Irishman was the Hibs manager's first signing in December 2011 but has rejected the offer of a contract extension to agree a move to the League Two club.
The Leith side need to beat Celtic at Parkhead on Saturday and hope other results go their way to clinch a top-six spot in the Clydesdale Bank Premier League, before a William Hill Scottish Cup semi-final against Falkirk the following week.
And Fenlon will have no qualms about calling on Doyle's services in the final weeks if required.
"Eoin has agreed a contract (with Chesterfield)," he told Press Association Sport. "We offered him a contract five or six weeks ago and he turned it down.
"That's the decision he has made and we just have to get on with it.
"But he's very honest, when he gets on the pitch he works very hard for the team so I don't expect anything different from him."