Liverpool assistant manager Zeljko Buvac will not be involved with the first team until the end of the season for personal reasons.
The Reds are preparing for Wednesday’s Champions League semi-final second leg against Roma, having won last week’s first leg at Anfield 5-2.
There were reports Buvac left Liverpool after a falling out with manager Jurgen Klopp.
However, the Anfield club maintain Buvac remains a employee of the club.
Liverpool consider the matter to be private and say his position at the club will not be affected by his absence.
Buvac became Klopp’s assistant at Mainz in 2001, with the pair having been together at the club during their playing careers.
Klopp was appointed Borussia Dortmund boss in 2008 and took Buvac with him.
The pair helped the club win the Bundesliga title in 2011 and 2012 before he again joined up with Klopp, who was appointed as Liverpool manager in October 2015, at Anfield.
BBC Sport chief football writer Phil McNulty
The departure of Buvac is a serious blow to Liverpool and manager Klopp before their Champions League semi-final second leg against Roma in Italy on Wednesday.
Liverpool insist assistant manager Buvac’s departure is for “personal reasons” but the timing is what is most striking, just days before arguably the club’s most important game in years.
And for Klopp, it represented the loss of the man who has been at his right-hand side in management for 17 years at Mainz, Borussia Dortmund and then latterly Liverpool.
Buvac has been labelled “The Brain” for his input into coaching and tactics throughout Klopp’s management career, who insisted he had to be part of his management team when he arrived at Liverpool in October 2015.
He is the familiar long-haired figure next to Klopp in Liverpool’s technical area and has always been regarded as man with the expertise, credentials and close personal relationship to be able to play a key role in the German’s decision-making.
It remains to be seen whether Buvac returns after Liverpool revealed he would “spending some time away from the first team environment” – but the fact this absence comes at such a crucial time in the club’s season, with a top four place in the Premier League and the Champions League so high on the agenda, makes this open to question.
And it will also create an unwelcome distraction for Klopp and Liverpool when they went sole focus to be on events in Rome on Wednesday night.