The former European champions lie in seventh place as they prepare to host bitter rivals Lyon on Sunday, almost a month after Andre Villas-Boas was removed as coach following a row over transfer policy.
They have won just once in nine league games, jeopardising their chances of qualifying for Europe next season.
Meanwhile, the club is still reeling from the violent January attack on their training ground by several hundred protesting supporters.
Organised supporters groups are also calling for unpopular president Jacques-Henri Eyraud to resign.
Into this volatile atmosphere is expected to walk Sampaoli, the 60-year-old Argentine who coached his country at the 2018 World Cup and this week announced his departure from Brazilian club Atletico Mineiro.
Sampaoli previously won the Copa America with Chile in 2015 and spent a season in Spain with Sevilla.