Sable took charge when Oscar Garcia was sacked last month, but Les Verts have been fined 25,000 ($29,697) for every game played with the 37-year-old in charge.
Saint-Etienne are on a 10-match winless streak and a 4-0 thrashing at home by Monaco last Friday saw them fall to within two points of the Ligue 1 relegation play-off place.
Gasset was briefly Montpellier’s head coach last season after the sacking of Frederic Hantz, but that was his first top job in the French top flight since leaving the same club in 1999.
“The club is relying on the experience of Jean-Louis Gasset to redress a delicate sporting situation,” the club said in a statement after naming their third coach of the campaign.
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