Following Saturday's 4-0 thumping at the hands of Tottenham Hotspur, Bielsa is thought to be on the brink of an exit from Leeds after nearly four years with the Whites.
The 66-year-old's side have lost each of their last four in the Premier League - conceding 17 goals in the process - and are only two points clear of the relegation zone having played two more games than 18th-placed Burnley.
According to journalist Fabrizio Romano, lawyers are in the process of negotiating Bielsa's exit from Leeds, who are "close" to welcoming Marsch to the club as his successor.
The American enjoyed a successful two-year stint with Red Bull Salzburg before replacing Julian Nagelsmann at RB Leipzig, but he only won seven of his 20 games in charge and was sacked in December.
Bielsa has now taken charge of 170 matches for Leeds since arriving in 2018 - winning 81 of them and achieving promotion to the Premier League with 93 points in their triumphant 2019-20 Championship campaign.