The American disclosed Ayling's recent surgery for the first time during his pre-match press conference ahead of this Sunday's fixture versus Brentford.
"Luke Ayling had successful surgery yesterday so based on how the surgery went, we're hopeful that it's not too long, somewhere between 2-4 months to see how that progresses but it's a knee issue that he had to get sorted out, so we've decided to take this time to get him healthy," Marsch said.
A statement from Leeds United explained the decision for Ayling to go under the knife at this stage of the season, given the three-match suspension which will keep him out of the final game of the season.
"At the time [September], after discussions with some of the UK’s best knee surgeons, rather than full scale surgery, it was decided the area would be tidied up which would allow Luke to play until the end of the season.
"He returned to action in December, going on to make a further 22 appearances for the Whites in all competitions.
"Now Luke’s season has finished, the decision to progress to more definitive surgery has been taken and it is expected he will return to training in the Autumn."
Ayling will return shortly after the beginning of next season, which is scheduled for the first week of August - if Leeds remain a Premier League club.
If the team drop into the Championship, their league campaign will begin on the final weekend in July to accommodate for the 2022 FIFA World Cup in Qatar later this year.