Wigan boss Warren Joyce is recovering from minor surgery with assistant coach Graham Barrow placed in temporary charge, the club have announced.
Joyce, 52, had an operation on Tuesday following a routine medical examination on Monday and may not be well enough to take charge of Saturday's Sky Bet Championship clash with relegation rivals Blackburn.
Barrow told a press conference on Friday morning that it was "a serious health issue".
"The club can confirm that manager Warren Joyce underwent surgery on Tuesday for a minor but important procedure which required immediate attention," read a statement on the club's official website.
"He will not be taking training (on Friday). The plan is for him to be in attendance in some capacity at Ewood Park for the match versus Blackburn Rovers.
"In the meantime, Graham Barrow and (first-team coach) Andy Welsh will be in temporary charge of the team and will be communicating with Warren as much as possible.
"We expect Warren to make a full recovery very soon and will continue to offer him all the support he requires."
Barrow said: "I've spoken to Warren (on Friday) morning. I can't go into too much detail but it's as serious as any health issue can be."
Joyce left his role as Manchester United Under-21s boss to take charge of Wigan in November last year after Gary Caldwell had been sacked in October.
The Latics are currently second from bottom of the Championship after only one win in their last seven league games.
Victory over Blackburn, one place above them in the table, could lift them out of the relegation zone.