Steve Bruce and Bryan Robson do not make good enemies. They are far more comfortable sitting in a pub together, laughing and joking about anything other than football, and perpetuating a friendship that goes deeper than their pockets.
They are Geordies, they played together for Manchester United, and they share an urban sense of humour.
But this is the real world and today, in the cauldron that is The Hawthorns, Bruce and Robson will be out to prove that affinity and antipathy can be interchangeable. Friendship disappears for 90 minutes.
West Bromwich Albion versus Birmingham City is not traditionally a derby that provokes intense passions - the fans might actually like each other - but that will change when the teams kick off at 12.15 this afternoon.
Defeat for Birmingham, and suddenly the perception grows that Bruce is a manager under pressure. Defeat for Albion, and suddenly the perception grows that their good start to the season might only have masked an impending battle against relegation.
A draw, and nobody will be happy.
In a funny sense, Albion did best out of the matches between the teams last season. Even Birmingham?s 4-0 victory at St Andrew?s in December seemed to benefit Albion more, for they used the defeat to their advantage after that.
By the time Albion defeated Birmingham 2-0 at The Hawthorns in March, Robson?s team possessed a momentum that lasted right until the final day of the season. One might argue that Birmingham need the points more today, for anything less than a victory would present the obvious question: just why has Bruce failed to turn all those millions of pounds into a team capable of challenging for Europe?
He will, rightly, blame injuries and bad luck, but every team suffers like that. Liverpool won the European Cup last season after suffering their worst injury crisis in years. Not that Bruce uses the injuries as an excuse but he does accept the mantra ?to whom much is given, much is expected?.
Birmingham are at the crossroads. This is the strongest squad in their history yet there are no signs yet that they can emulate the 1956 team that won one of the leading honours.
Last season, they were expected to defeat Albion and surprisingly lost at The Hawthorns. This time, the picture is different. Albion are stronger than they were in March but that is not what makes them such a different proposition.
It is the confidence, instilled by Robson, that makes the team capable of so much. Whereas Birmingham play nervously, Albion play with little fear of defeat.
So they lost 4-0 away to Chelsea in midweek but they will not be the first to suffer in that way. Besides, they might actually benefit from such a reality-check.
But today might all be about one man: Geoffrey Malcolm Horsfield.
The former Birmingham striker has scored two goals in one match for Albion this season and is so popular at The Hawthorns that club officials even let him turn up for matches in his brown felt suit.
If this was a script, Horsfield would score a hat-trick in a 3-2 win and prove that Bruce was wrong to let him leave Blues. Ideally, Bruce would have kept Horsfield but he had to sell the striker to fund a package to sign Mikael Forssell.
Even Horsfield saw the logic in that.
Horsfield is lucky. Not long after he joined Albion, Robson took over as manager and they have thrived in each other?s company. Horsfield has just signed a two-year contract and, at 31, might still have his best days ahead of him.
Bruce has nothing but kind words for Horsfield but there is bound to be a deep-seated fear that, just as Andrew Johnson scored the winning goal for Crystal Palace against Birmingham last season, so Horsfield will do likewise for Albion today.
And then there is Darren Carter. The Albion midfielder, who emerged from the Blues youth academy into the first team, was stunned to be sold by Birmingham in the summer in surely one of Bruce?s most surprising decisions.
Carter has yet to play for Albion but today would be the ideal occasion for a debut; another opportunity to prove Bruce wrong.
Whatever happens, the final whistle will allow Bruce and Robson to embrace like brothers, but the preceding 90 minutes are what matter most.
The score? Probably a draw that will benefit nobody.