When it came to guessing which of the Manchester clubs would blink first it was always worth remembering that Sir Alex Ferguson's sides could outstare a cobra.
Before an ultimately one-sided contest began the Manchester United manager announced he wanted to "ignite the chemistry that exists between ourselves and the supporters. It is a potent formula."
The match itself did not produce the heat of an average Bunsen burner but, when the news came through that Swansea had found the net against Manchester City, the excitement rolled around Old Trafford with the sound of an Atlantic breaker. They were standing up for the champions.
No scanning of the fixture list in June can predict when the season's decisive moment will come. Arsenal blew two title challenges at Bolton in 2003 and Birmingham five years later and this had a similar feel of a tipping point.
Two seasons ago, Wayne Rooney found the net 34 times, which did not impede Chelsea's relentless march to the Double at all. This time, he has 26 and it is now more than likely that it will be rewarded with significant silverware.
This, however, was a more difficult fixture than it looked. Last season, West Bromwich Albion were the only team to take points from Manchester United at Old Trafford and they came into this match on the back of two victories, against Wolverhampton and Chelsea, that resulted in their opponents' managers being fired.
West Bromwich resisted reasonably well until Rooney broke through from nowhere. Once Jonas Olsson's second yellow card had reduced them to 10 men with nearly half an hour remaining, Roy Hodgson's main thought had been to get his team on to the southbound M6 without a hammering. In this he succeeded. "There are not many teams of our ilk who come here and put Manchester United under enormous pressure," he said. "If you do get a result here, you do it with a tin hat on."
What differentiates the great sportsmen is their ability to see a ball or an opportunity fractionally before their opponent. When Paul Scholes delivered a lovely chip over the top to Javier Hernandez, the Mexican unleashed what may have been a cross but could have been a shot. It was either going into the advertising boards or the keeper's gloves. Instead, Rooney anticipated its flight and met it just before the goalkeeper. It was extraordinarily good, so much so that Ferguson thought his forward must have been offside.
In Europe, Manchester United have seemed horribly fragile – Basle, Ajax and Athletic Bilbao, good teams but not part of Europe's elite, have scored eight times in three matches here. However, in the Premier League at least, the old aura has returned.
"I don't think we have had the credit we deserved over the last few months," Rooney said. "Europe has been disappointing, fair enough, but we have played well against the big teams recently and, though we have not always been at our best, we are where we want to be." This may have been the decisive day but the decisive results had come in London, at Arsenal, Chelsea and Tottenham – games that at Eastlands they might have expected United to lose.
Here, much of Manchester United's real creativity came from the boots of Ashley Young but whenever Rooney intervened, West Bromwich suddenly and significantly looked threatened.
Immediately after Peter Odemwingie had made a bid for the most flagrant dive of the season – although Hodgson thought Patrice Evra had fouled his forward – Rooney broke away lethally. He fed Hernandez, who drove a shot hard against Ben Foster's post in front of the Stretford End.
Then another long, teasing ball from Scholes evaded both Hernandez and Foster and found Danny Welbeck facing goal at a tight but not impossible angle. However, the shot was pushed wide and Ferguson ran his hands through steel-grey hair. "It was worrying," he reflected afterwards. "If you don't score the second to take the pressure off, then you start to think all kinds of things will happen."
His anxiety would have shifted up a level when Lee Probert, having dismissed Olsson, rejected two penalty appeals for a tackle on Welbeck and a handball. Eventually, Keith Andrews bundled over Young and United got their penalty.
Rooney sent Foster the wrong way for goal 26. This game was over; the only question was how the one in Wales would end and the roar that crashed around Old Trafford told its own story.
Man Utd: DE GEA 7/10; JONES 6; EVANS 7; FERDINAND 7; EVRA 7; WELBECK 7; SCHOLES 7; CARRICK 6; YOUNG 8; HERNANDEZ 6; ROONEY 8
West Brom: FOSTER 7; OLSSON 5; McCAULEY 6; RIDGEWELL 7; MULUMBU 6; TAMAS 6; BRUNT 6; MORRISON 6; ANDREWS 7; FORTUNE 5; ODEMWINGIE 5
Substitutes: Man Utd Pogba 5 (Scholes, 72). Cleverley (Welbeck, 77). West Brom Scharner 5 (Andrews, 72), Shorey 5 (Brunt, 72), Long (Fortune, 77). Booked: Man Utd none. West Brom Olsson. Sent off: West Brom Olsson (66). Man of the match Young. Match rating 5/10. Possession: Man Utd 55% West Brom 45%. Attempts on target: Man Utd 9 West Brom 1. Referee L Probert (Wiltshire). Attendance 75,598.