Fabian Delph told Keane once ‘Don’t try to f****** mug me off,’ after being criticised by the Irishman during a training session in July

Feud sparked when Agbonlahor allegedly tried to belittle Keane after No 2

Roy Keane and Gabriel Agbonlahor almost came to blows in an explosive training ground bust-up that hastened the Irishman’s shock departure from Aston Villa.

Sportsmail can reveal the real story behind Keane quitting his post as Paul Lambert’s assistant a fortnight ago, after just six months in the job. He had festering disputes and disintegrating relations with key Villa players. Morale around the club’s Bodymoor Heath training ground had sunk so low that news of his exit was welcomed by the majority of the squad.

A source said: ‘The atmosphere was horrible. It went downhill the moment Keane arrived. He p****d off all the big names he shouldn’t have p****d off and his relationship with the senior players slowly fell apart.

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Roy Keane quit as Aston Villa's assistant manager last month, after reportedly leaving a negative atmosphere

‘There was so much gloom about the place every time he turned up. When he went there was just a feeling of euphoria and relief.’

Months of simmering tension came to a head when Keane clashed spectacularly with stand-in skipper Agbonlahor in front of stunned team-mates in training days before the Irish assistant’s departure was confirmed.

It is understood the long-serving Villa star was talking tactics with Lambert when Keane interrupted. Agbonlahor resented the interference and tried to belittle Keane by telling him: ‘Excuse me, but I’m talking to the boss!’

The two men then became involved in a heated row and had to be separated. The ill feeling continued after the training session and Lambert held talks with Keane in the afternoon when it was decided they would part ways.

Gabriel Agbonlahor (left) and Keane had an explosive argument in the build-up to his resignation

This was the last in a series of flashpoints which resulted in Keane alienating himself from the players.

They began soon after his arrival in July when Fabian Delph objected to criticism from the former Manchester United captain in training and rounded on him in front of the rest of the Villa squad.

The England midfielder, who is said to have taken an instant dislike to Keane, screamed: ‘Don’t try to f****** mug me off.’ Their relationship never recovered.

The 43-year-old hardly endeared himself to his new squad after a 1-0 home defeat by Leyton Orient in the Capital One Cup in August when he berated the players in the dressing room afterwards, and told them: ‘If I gave you 10 grand, you couldn’t even score in a brothel!’

Keane is also understood to have laid into the team when Lambert kept them in the dressing room for an hour after a 2-0 defeat at QPR in October. Defender Chris Herd is another of the players said to have had a falling out with the brooding Irishman, who became exasperated with the relaxed attitude to training by some other players, including Charles N’Zogbia.

Fabian Delph's (centre) relationship with Keane never recovered after a training ground bust-up in July

And Keane was also exasperated with the attitude of Charles N'Zogbia (centre) in training

‘It was a combination of row after row and none of them were in private,’ our source told Sportsmail.

‘The problem with Keane is that he demands the same standards that he was used to at United and the lads at Villa don’t get paid enough to put up with that kind of c**p. He just got everybody down.’

The obsessively punctual Keane would leave his Cheshire home at 6am to be at Bodymoor Heath in time for training, and there were players at Villa who liked his attitude as well as his training methods.

However, the atmosphere was so poisonous by the end that few were sad to see him go. Relieved players exchanged texts when they were informed ahead of the official announcement on November 28, and the mood on the team bus to Burnley the next day was said to be significantly better than in previous weeks.

Villa strongly deny Keane left the club due to disagreements with players, or that Agbonlahor was involved in any row.

Keane's (right) departure was allegedly welcomed by Villa players ahead of their game at Burnley last month

The official reason given for Keane’s departure is that he was finding it difficult combining his work at Villa with his job as assistant manager with the Republic of Ireland.

That has been met with widespread scepticism, however, considering that Ireland do not have another game until March. It also seems odd that Keane left a day before the game at Burnley and questions about the matter were strictly prohibited in Lambert’s post-match press conference at Turf Moor.

The Villa players have also been sworn to secrecy over the real reason behind Keane’s exit, but our revelations today will come as little surprise to those who have followed his controversial career.

As a player, his fastidiously high standards led to the infamous row with Mick McCarthy in Saipan over Ireland’s training camp for the 2002 World Cup and Keane being sent home from the tournament.

He departed United three years later shortly after a similar falling out with Sir Alex Ferguson and Carlos Queiroz on a pre-season trip to Portugal.

Keane's (right) left Manchester United as a player after an argument with Carlos Queiroz (centre) in 2005

Keane’s friend and former Ireland team-mate Paul McGrath, who spent the majority of his career at United and Villa, admits his compatriot struggles to get along with people who do not match those standards.

McGrath told Sportsmail: ‘Roy says it as he sees it and doesn’t have too much interest in respecting big personalities or trying to be nice to people he can’t be bothered with.

‘If he doesn’t agree with you, he will tell you in no uncertain terms and that can rub people up the wrong way.

‘He has high standards, good standards, that make those around him better and if you don’t want to follow them I’m not sure he has time for you. That’s no bad thing when you consider what he has to offer and what he has achieved.’

The intensity of Keane’s management style is laid bare in his splendidly candid autobiography The Second Half, published in October, which includes details of his time in charge of Ipswich and Sunderland.

Keane released his controversial second autobiography 'The Second Half' in October

He confirmed that his falling out with Ipswich captain and Republic of Ireland international Jon Walters over concerns the player was angling for a move to Stoke in 2010 involved some ‘effing and blinding, a bit of shoving’.

The two men have made up since Keane took over as No 2 to Ireland manager Martin O’Neill, but it’s understood the row was so heated at the time that Walters warned Keane that he knew where he lived. The Ipswich boss then grabbed a pen and paper and handed the player his address just in case.

It came to a head after Walters withdrew from a League Cup tie against Exeter in 2010 due to a stomach bug, and Keane demanded the player provide Ipswich’s medical staff with evidence.

‘I sent the physio a photo of my sick,’ recalls Walters. ‘He came round at eight o’clock the next morning with the club doctor and said that he could smell (on my breath) that I’d been sick.

‘You never know where you stand with him and that was the fear factor he brought in. I respected him as a player, but maybe he can’t get his point across as a manager.’

Stoke forward Jon Walters has mended his relationship with Keane, following their time together at Ipswich

In his book, Keane admits: ‘I don’t think I’m a bad manager, but at Ipswich I managed badly. I spoke to some people like something on the bottom of my shoe.’

The combative streak that made Keane a great player just didn’t seem to work for Keane the manager. Defender Gareth McAuley — now at West Brom — describes a pre-season army camp arranged by the manager.

‘That was horrendous,’ says McAuley. ‘He took our phones and wallets away from us, saying, “You’ve got five minutes to phone home and say you won’t be home tonight”.’

At Sunderland, where Keane won promotion to the Premier League in his first season in charge, it was alleged that he slapped his captain Dean Whitehead during the half-time interval of a League Cup tie against Northampton Town in September 2008 after sending the tactics board flying with a kung-fu kick.

With more time on his hands now, Keane was back in his hometown of Cork this week signing copies of his autobiography.