That gives Vladimir Romanov, the owner of Hearts, just over three weeks to find his seventh permanent manager in as many years.
Sergio, who replaced Jim Jefferies last August, said he could not accept a "huge cut" in his salary to remain at the club and his exit was announced on Thursday.
Falkirk's Steven Pressley, Cowdenbeath's Colin Cameron, and Paul Hartley, the manager of Alloa Athletic, have been linked with the post and all played for the club, but Romanov's appointments have often come out of left field. Portuguese coach Jose Couceiro, who has managed FBK Kaunas and the Lithuanian national team, and is known to Romanov and his advisors.
"It's a must that we have someone in before pre-season," said Fedotovas. "We have a preliminary short list. We have not spoken to anyone as we had hoped that things could have been sorted positively with Paulo Sergio. Now the process will start. It is a very attractive job with the added incentive of European football again. We are expecting lots of candidates.
"We are open-minded when it comes to . . . a new manager, we are not bothered about their nationality. It's about a person that brings true professionalism to the club and someone that can match the ambitions and goals we're looking to achieve."