Francois Ciccolini has been tasked with securing Bastia's Ligue 1 status after he succeeded Ghislain Printant at the helm this week.
Printant was relieved of his duties after a poor run of results over the past three months, where Les Bleus had won just three of their last league matches.
The 1-0 defeat at Guingamp was the final straw for the club's hierarchy, which came just four days after they were dumped of the Coupe de France by Ligue 2 side Sochaux.
The Frenchman's assistant, Ciccolini, has now been handed the reins on an interim basis until the end of the season and he will take charge of proceedings for the first time against Lyon on Saturday at Stade Armand Cesari.
"From today Ghislain Printant is no longer in charge of the professional team," a statement from the Corsicans read.
"Francois Ciccolini has been given the task of filling the role on an interim basis until the end of the season and to ensure the club stays in Ligue 1.
"More details on the reasons for this internal reorganisation will be given tomorrow at the pre-match press conference."