Louis van Gaal and Ronald Koeman feud alive, well and much worse after wine snub

And the sourest relationship in sport apparently took a turn for the worse last season.

The Daily Mirror has run an interview with Koeman in which he explains that the two men fell out over a couple of glasses of wine last season.

When Southampton entertained Manchester United at St Mary's on a chilly night in December, Koeman graciously invited Van Gaal for a glass of wine despite the Saints having been beaten - but his former mentor told him he was too busy.

The return match was just a month later - and this time, Southampton won. Van Gaal returned the compliment by asking Koeman for a glass of wine - but after keeping him waiting around, Koeman assumed he'd been stood up and walked away to catch the team bus.

"At St Mary's he was lucky to win. Still, the wine was ready but Louis said he didn't have time to come in.

"We went to Old Trafford and won, Louis said to me, 'Your glass of wine is waiting, I will come in a minute.

"I waited for a quarter of an hour but apparently he was busy with the press.

"So I said, 'Give Louis my regards.' I started to walk to the team bus when Louis came out.

"'What about the wine?' he said.

"'I have to go, Louis,' I answered. 'Just like you that time at St Mary's."

The pair's history goes back to the 1990s, when Van Gaal brought Koeman in as one of his assistants at Barcelona - and the two initially got on famously, with Koeman becoming Van Gaal's protégé.

Sadly, things went sour after that. At times Van Gaal's star has been in the ascendancy; at other times, Koeman has outshone the man who brought him in to club management. We take a look at the key moments when their careers have crossed paths.

Koeman retired from playing in 1997 and quickly joined Guus Hiddink's staff for the Dutch national team at the 1998 World Cup. After impressing with his efforts in France, Koeman got a call from Van Gaal to come to Barcelona where he worked as an assistant for two years, helping Barca to the 1999 Liga title. But things went sour for the Catalan club in 2000, with Van Gaal leaving - and Koeman having little choice but to find a new job.

After a short and successful spell at modest Vitesse Arnhem, Koeman took over at Ajax and immediately led the club to a domestic double in 2001-2002. Koeman's team won the Eredivisie again in 2004 - but the seeds of disaster had been planted early in 2004 when Van Gaal was appointed as Ajax's technical director.

Van Gaal was a club legend having led the side to Champions League glory and was supposed to concentrate purely on buying and selling players, leaving the team management to his former assistant.

But Louis just couldn't swallow it: "At every training session Van Gaal would take a chair from his office and take a seat right next to the training pitch," Dutch football journalist Elko Born wrote in Four Four Two.

"There, he’d sit and judge the players Koeman was coaching. On a few occasions, the director of football would start applauding the players he liked most."

That's not all: on one occasion, Van Gaal actually stepped out of the stands during a match and called the young Zlatan Ibrahimovic over to tell him to attack the far post more at corners. Ibrahimovic and Koeman were both furious at the intrusion - but reportedly even more irked when the instruction worked, leading to a Zlatan headed goal and an ostentatious bit of fist pumping from the interfering technical director.

It was another episode surrounding Ibrahimovic that really blew the argument up, however: the young Swede had been a sensation in the Eredivisie and Champions League, and Koeman was utterly determined to hang on to him.

But Van Gaal had other ideas. He flogged him to Juventus on the last day of the transfer window, leaving Koeman with no star striker and no time to bring in a replacement. The €16 million fee, Koeman raged, would come to seem cheap in retrospect. How true that proved.

The simmering tempers spilled over: Koeman went to the board to complain and, according to Van Gaal, later admitted feeding negative stories to the media to try to get his former mentor sacked. Van Gaal retaliated by going on record to blast Koeman's tactics, claiming that the team had abandoned "the Ajax way" and turned its back on total football.

The pressure worked, for both men: Van Gaal went first, resigning in October (with a nudge from the board) but Koeman went three months later as his team - understandably, struggling without their best player - fell off the pace in the league and went out of Europe.

But it was Van Gaal who lost that power struggle, and Van Gaal who sounds bitterest.

"Ronald Koeman engineered my departure from Ajax with support from within the club and help from the media,” Van Gaal later said in a television interview.

“I asked him whether he had deliberately used the media and his answer was yes.”

Van Gaal probably came out worse of the Ajax debacle - and his revenge took a long time coming. He took his next job at AZ Alkmaar, quickly leading them into Europe and second place in the league - but Koeman took over at PSV Eindhoven in 2006-07 and won the title in his first season in charge.

It was a new humiliation for the master being bested by the apprentice, but Van Gaal made up for it: Koeman was poached by Valencia, while Van Gaal led AZ to the Dutch title in 2009 before Bayern Munich came calling.

The replacement for Van Gaal? Ronald Koeman, who should have done a good job. He'd won the Copa del Rey with Valencia (though they struggled in other competitions) and took over an AZ team with the best defence in the division, and the second-best attack. But his tenure lasted just a few months as he was fired after losing seven of his first 16 matches. Given that his squad was pretty much unchanged, it tarnished Koeman's reputation badly - he didn't get another job for nearly two years.

Koeman's next job was at another Dutch giant, Feyenoord, which required plenty of contact with Van Gaal since he was by then the national team coach; five of the Dutch team in Brazil were Feyenoord players, while the national side used the same 3-5-2 system that Koeman's outfit favoured - a decision that was at least inspired by Koeman's team.

The two managers got back on speaking terms and did at least shake hands last season - but as Van Gaal put it, "I'll never have dinner with him again."

But as the wine story above shows, the simmering resentment appears to be anything but dead.

Were the offered glasses of wine truly olive branches? Or just the Premier League managers' equivalent of that playground game when you offer a handshake only to pull it away at the last minute? Who knows, but we're genuinely looking forward to the next instalment of this particular grudge match.