Brian Kerr: A bitter rivalry is taken to another level by Mourinho and Klopp - two of the game's most charismatic characters
A poisoned gift", said Jose Mourinho after discovering Manchester United's game with Liverpool had been scheduled for the start of a ten-day period in October that also saw them meet Fenerbahce in the Europa League, Chelsea in the Premier League and Manchester City in the League Cup.
And you can understand his choice of phrase. Having been in England long enough to understand the depth of the rivalry between these two clubs, Mourinho could see both the benefits and pitfalls of meeting Liverpool at that particular time.
This was mid-October and United had won just once in the league since August, when they were so significantly inferior to City in their first real test of the season.
In danger of drifting completely off the pace that was then being set by Arsenal as well as City, Mourinho knew they couldn't afford to lose that game at Anfield. And they didn't - falling into the default position the Portuguese so often uses when his back is against the wall.
Back then, when the manager was complaining about living in a hotel, and the lack of anonymity around Manchester, there were people wondering if Mourinho would last the season.
His problem was that he didn't know his best team. Or his best system. So heading to Anfield on that Monday night, there was only one thing in his head: avoid defeat.
Which they did. Amazing then, that three months on, so much has changed. For a start, Mourinho seems happier, both within himself and with his team.
Having started the season seemingly with pre-conceived notions, he has shown the wisdom to change his mind about a number of players who are now key men in his team.
Michael Carrick is one of those. Ignored until the week after that Liverpool game, when he was catapulted into the starting XI for the League Cup clash with City, the veteran midfielder has been a regular ever since.
His guile, composure and experience give structure to the team, while allowing Mourinho find a formation that combines the cavalier approach expected of United teams with the manager's inherent pragmatism.
It is Carrick's positional intelligence that ensures the side has a defensive solidity, while allowing Paul Pogba to operate in a more offensive role, which he has done to great effect ever since the 35-year-old's re-introduction to the United starting X1.
The busy nature of Ander Herrera's play, coupled with Pogba's overall improvement, has altered the mood inside the club. Last year, as United registered 3,222 backward passes - and recorded the fifth lowest number of attempts on goal in the Premier League - chants of "attack, attack, attack" provided the soundtrack for many games at Old Trafford.
Now the image is completely different.
United are having a go again, and never was this more obvious than when they played Middlesbrough on New Year's Eve and were trailing to Grant Leadbitter's goal. Under Louis van Gaal, patience would have been the preferred approach.
Here, under Mourinho's watch, they were bold - a 4-3-3 formation making way for a reckless 2-2-6 approach with Juan Mata sent on for Marouane Fellaini, Marcus Rashford replacing Chris Smalling.
The gamble paid off, Anthony Martial equalising with five minutes left shortly before Pogba headed the winner from Mata's delicious cross.
By now, it was clear that Mourinho had divided his squad into two parts. Eight are regulars: David de Gea, Phil Jones, Marcos Rojo, Antonio Valencia, Zlatan, Herrera, Carrick and Pogba while another group contains players who are rotated. Some of those players in this secondary grouping - Wayne Rooney, Mata, Henrikh Mkhitaryan, Rashford, Fellaini, Martial - come with either big reputations or big transfer fees, yet Mourinho seems prepared to deal with whatever issues his policy may create.
"He's a different person," Mata said earlier this week of the manager who sold him to United from Chelsea back in 2014.
In fact he seems a different person to the man who had a face on him like a robber's dog in October.
The smile is back and the loutish behaviour we sometimes saw when he was at Madrid or Chelsea has been absent - almost as if he has placed a silencer on his tongue and is editing his comments to reflect the club's historical preference for a more diplomatic and less combative leadership.
And the fascinating aspect to all of this is that in his search for an effective combination of players, he has been prepared to give a chance to guys who you thought had been written off.
There's Mata, the player he once sold; Carrick, who he had ignored throughout August and September; Mkhitaryan, who he took off at half-time against City, less than two months after paying £26mfor him. Then there are Jones and Rojo, who didn't appear to have a future at the club but who are regulars now.
Beyond this, his man-management has been fascinating to watch. He backed Fellaini when the crowd turned against him - and was rewarded with a crucial goal (and a huge hug) against Hull in midweek.
In addition, he also showed support to Zlatan Ibrahimovic during his lean period, when he scored just one goal in 11 games. "He's still playing well, the goals will come," Mourinho said.
And they have, 12 arriving in the last 12 games. Others, like Pogba and Herrera, have been cajoled into delivering better performances than they produced early in the season, while Mourinho's ability to rotate many of his attacking players has also been a successful ploy, with Martial getting that vital goal against Middlesbrough, while Mata and Rashford have also made sizeable contributions.
With harmony achieved, results have been good. Nine wins on the trot suggests a corner has been turned - yet when you look at the quality of the opposition they have defeated, an asterisk needs to be placed beside those stats.
With the exception of their 1-0 victory over Tottenham and their 2-0 win at the Hawthorns against West Brom, the other seven conquests on this winning streak have been against teams who are either weak or in disarray: Hull, West Ham, Sunderland, Palace, Middlesbrough, Zorya and Reading.
It's worth noting, therefore, that in matches against fellow members of the Premier League's top six, United's results have been much less impressive. City outplayed them and Chelsea humiliated them; Arsenal left Old Trafford with a draw, and Olivier Giroud's last-gasp goal was one you could never have imagined a team managed by Mourinho circa 2009 conceding.
Their only win, of note, then has been against Tottenham, which is one of the reasons why tomorrow's match is of such importance to both Mourinho and the club.
"We have to do better, the crowd have to do better," he said on Tuesday, after their win over Hull in the League Cup semi-final. "It is not the theatre."
Yet we can expect plenty of drama tomorrow - not to mention an enthralled audience, filled with patrons whose contempt for one another has been unhealthy at times, especially when distasteful songs have been sung by opposing fans about the Munich and Hillsborough disasters.
It's always been an issue of intrigue, this rivalry, because while it can be partially explained by the geographic proximity and socio-economic contests between the cities, it is worth noting that the police presence at Goodison Park tomorrow, where Manchester City travel to take on Everton, will be nowhere near as strong as the security at Old Trafford.
It simply doesn't have to be, because the Everton-City dynamic bears no similarities to the bitter United-Liverpool relationship.
Had Everton and City extended their dominance over English football, which lasted only for a brief period at the end of the 1960s, when City won the league in 1968 two years before Everton claimed the 1970 title, then maybe this would be the north-west derby we'd be focusing on in greater detail.
Instead, it's Old Trafford rather than Goodison Park where our concentration will be most intense tomorrow, as Liverpool's period of 27 years without a league title evokes memories of the period from 1967 to 1993 when United failed to win England's top division.
As they struggled, Liverpool became the country's - and on four occasions the continent's - dominant side before Alex Ferguson's prophetic statement about knocking the Merseysiders off their perch came true.
So each club's era of dominance has coincided with a barren spell for the other side
While there have been periodic uprisings from other clubs over the course of the last 50 years - particularly from Leeds and Nottingham Forest in the '70s - only Arsenal and more recently Chelsea and City have interrupted the flow of success for a significant length of time.
No-one, though, can dispute the fact that these two clubs have been English football's most dominant ones.
Can Liverpool, inspired by Jurgen Klopp's magic, achieve the ultimate success again this season? Win tomorrow and you'd say they might. They can afford to draw this game whereas United can't.
Winning streak or not, the Red Devils are still 10 points adrift of Chelsea and have no margin for error left.
They need three points here and against a defence containing Ragnar Klavan and James Milner, with a dodgy keeper behind them, they have every chance.
While that may seem harsh on Milner, who has been outstanding this season as an attacking left-back, I suspect Mourinho will have a plan to expose his defensive frailties.
That said, Klopp will be also looking at United's right side, and in particular at the space Valencia often leaves behind by his regular forward forays.
He will look to Coutinho to change the game, Mourinho to Zlatan - all of which makes for exciting theatre.