Everton manager Ronald Koemanhas revealed he clashed with former Manchester United manager Louis van Gaal during their time together at Eredivisie club Ajax.
Koeman spent four years at the club as manager, having previously played for the Dutch giants as a player during the 1980s, and won the league twice, as well as the KNVB Cup.
Recalling his time in his homeland as Ajax manager, Koeman revealed he often clashed with former Barcelona and Netherlands manager van Gaal, who had joined the club as a director of football in 2004.
I got a problem with Louisin Ajax, Amsterdam," Koeman toldBBC Sport.
"He came back to Holland to be the director of football in the club, and we had really strong fights about the way of playing, about the future of the club.
"It wasn't really nice at the time but OK, that was the problem but OK,we shake hands and we don't see each other outside of football.
"We are not the best friends."
Van Gaal ultimately left his role a year later, with many citing the frequent conflict with Koeman as the chief reason for his departure.
Since leaving Ajax, Van Gaal has enjoyed numerous roles in management, winning the Eredivisie with AZ Alkmaar, the Bundesliga with Bayern Munich before guiding the Netherlands to third place at the 2014 World Cup and winning the FA Cup with Manchester United before being replaced by Jose Mourinho in the summer.
Koeman achieved most of his managerial success with Ajax, but has earned plaudits for his style of play and player recruitment during his time in England, leading Southampton to their highest ever Premier League finish of sixth last season, helping them achieve Europa League qualification, while his new club Everton have been tipped by some to potentially challenge for a Champions League place this season.