It has been a source of regret for Neil Warnock that he has had to wait a year to get another chance to cause an upset against Chelsea.

Tomorrow night his Leeds side will reach the semi-final of the Capital One Cup if they can beat a Chelsea team suffering from jet-lag and a lack of confidence following their failure at the Fifa Club World Cup in Japan.

Understandably, the 64-year-old has been excited about the tie since the draw was made seven weeks ago but it has also caused him to look back on the past with much anguish.

It is 14 months since the then Queens Park Rangers boss engineered a 1-0 win over the millionaires from Stamford Bridge.

For Warnock it was arguably the greatest win of his managerial career but less than three months later he was sacked.

QPR had suffered a dip in form, yet they were still clear of the Premier League’s bottom three and considering he took the club from Championship strugglers to promotion in just over a year, one might have expected ­Warnock to be given the chance by chairman Tony Fernandes to strengthen the squad in the January transfer window.

Instead, just eights days into 2012, he was replaced by Mark Hughes, who went on to spend a fortune during a woeful 10 months, which brought only six wins in 30 League games.

Rangers are now facing a real challenge to beat the drop and, significantly, new boss Harry Redknapp has turned to many of Warnock’s signings such as Shaun Derry, Clint Hill, Jamie Mackie and Adel Taarabt, to get them out of trouble.

That has made his memories of his time at Loftus Road all the more bittersweet and he told Standard Sport: “Tony and the owners had their own ideas so you can’t blame them for that — I just think they lost the soul of the club when I left. It became a club for mercenaries.

“I felt the staff and me did a miracle job to just keep them in the Championship and then, to get a promotion-winning team. I deserved more loyalty.

“But there were certain individuals who became too influential on pushing managers’ names forward, players’ names forward and the board got sucked into spending a lot of money they didn’t have to.

“To have the carpet whisked away from under my legs was very unfair. In hindsight, they have wasted a lot of money and got nothing out of it. They’ve not got any better and are using my players rather than some of the millionaires.

“What happened was the most disappointing thing to happen to me in my career, more so than the way Sheffield United were relegated.”

That is some statement from ­Warnock, especially as he prepares to come face-to-face with Chelsea interim coach Rafael Benitez.

Warnock has always resented Benitez for fielding a weakened ­Liverpool team in a key game against struggling Fulham at the end of the season in 2007.

Benitez wanted to rest his men ahead of the Champions League Final two weeks later and Fulham took advantage by claiming a crucial win as they ended up finishing above Warnock’s Sheffield United by one point.

You get the impression Warnock would love to talk more about it but Benitez reportedly sent him an email threatening to sue him if he did.

Benitez has bigger problems to worry about right now. The Chelsea fans are still calling for his dismissal and his impact on the team since he replaced Roberto di Matteo has been limited.

Though he may not say it publicly, Warnock certainly senses an opportunity for revenge. He added: “I’ve never been in a position like Benitez where the fans have been against me from the start like he’s got now. I’ve never had hostility like he’s got there.

“I wish I’d got those players to work with, they’re fabulous. They have two teams who can quite easily play in all the competitions and do well.

“Obviously, I know how to beat Chelsea from what I did with QPR last year and I will take some of the lessons from that game into this one.”

There is just one significant difference and that is Warnock has an eye on a big Championship game against ­Middlesbrough at the weekend and is considering rotating his squad. He hopes to win promotion with Leeds this season so that he can take on the Blues more regularly.

However, former Chelsea and current Leeds chairman Ken Bates would enjoy inflicting more pain on his old club’s owner Roman Abramovich and is keen that Warnock plays a full-strength side.

The manager said: “Middlesbrough is more important to me personally and there are a few niggles I don’t want to risk. Ken wants to win the game more than anything and has tried to influence my team selection but I won’t let him affect that. But we will still give it everything and whoever wins, will have a great chance to win the competition. Chelsea are strong favourites. But every game is winnable for us.”

Leeds have already proved that by knocking out Premier League Southampton and Everton this term. Warnock said: “Everton put a strong team out and were gutted when we beat them. We have played well in every round but the victory over Everton was one of the best performances this season.”

But however good that victory was it still does not match up to the triumph over Chelsea last term. The Blues, then flying under Andre Villas-Boas before it all came to a sorry end, went into the match with only one defeat in eight League games.

Warnock said: “I think that win started his [Villas-Boas’s] downfall. No one coming to the game that day, including QPR fans, though we had a chance.

“All I kept telling the players was how we were going to beat them. I know they had two men sent off, but that didn’t help us, we actually played better 11 v 11. It was a fantastic day, to beat Chelsea when we were nearly getting relegated just over 12 months earlier, it doesn’t come much better than that.”

The stunning victory was overshadowed by the John Terry/Anton Ferdinand race row, which resulted in the Chelsea captain being banned for four-games by the Football Association.

The Blues were at the centre of another controversy this season when they alleged referee Mark Clattenburg racially abused John Obi Mikel. The FA cleared Clattenburg and gave Mikel a three-game ban and £60,000 fine for threatening the official. During the FA investigation, Warnock accused Chelsea of trying to “kill the referee”.

Today, though, he said: “They know they made a mistake and on reflection won’t be very happy with their actions. They’re bigger than that, but we all make mistakes. I don’t think there’s much wrong, it’s a great club.”