In any industry it is easy to chastise the man who chooses to stay in his comfort zone rather than test himself to the limits. Harry Redknapp seemed to put himself firmly in that category in January when, after much soul-searching, he rejected an offer to take charge of Newcastle United, citing the lifestyle he enjoys on the South Coast. But sometimes the family man is rewarded for putting contentment before single-minded ambition.

Even at 3.30pm on Saturday, slouching against a wall next to the directors’ lounge after Portsmouth’s first win at Old Trafford in more than half a century, Redknapp was continuing to cite family matters rather than football as the reason for rejecting the lure of St James’ Park. But by now, with his Portsmouth side having earned a Wembley FA Cup semi-final and strong favourites to win the trophy for the first time since 1939, he is on his way to realising ambitions that are far beyond the nightmares that are being experienced on Tyneside.

“To win the FA Cup would be fantastic for this club,” Redknapp said. “It was a difficult decision not to go to Newcastle. It’s easy for people to say I should have taken the challenge on. If I was 40 I might have done, but I didn’t want to be away from my wife and grandchildren and I’m happy with my decision, especially after a result like this.”

At the same time that Redknapp was talking, Sir Alex Ferguson was claiming a refereeing conspiracy, but when he sees his friend strolling out at Wembley next month – and, the bookmakers predict, in the final on May 17 – the Manchester United manager is unlikely to begrudge Portsmouth a victory they merited.

Rarely in recent years has Ferguson reacted to a United defeat with such a remarkable lack of grace, but, as Redknapp headed for their postmatch drink, it was hard to imagine that he would be greeted with anything other than warmth, a congratulatory handshake and the usual glass of fine wine.

Ferguson felt that Portsmouth were lucky. In some senses they were – lucky that Martin Atkinson, the referee, did not award United a penalty when Sylvain Distin blocked Cristiano Ronaldo and lucky that Michael Carrick failed to put the ball into an open net shortly before the decisive goal – but this was one of those occasions when good fortune is earned.

Redknapp’s team were prodigious in their workrate and, in the cases of Glen Johnson, Sol Campbell, Distin and Lassana Diarra, outstanding in their defensive work. Theirs was a victory that could be likened to the boxer who withstands a pummelling before surprising his opponent with a sucker punch, but, as Redknapp said, “you’ve got to ride your luck to have any chance here”.

You also have to compete. Diarra dumped Ronaldo on his backside in the opening seconds, with the United player complaining that he was “thinking of changing my game”, so unhappy was the winger at the lack of protection afforded by Atkinson.

This is a sensitive topic in the light of injuries caused by late tackles in recent weeks, but Ronaldo’s comments – and some of his histrionics throughout the afternoon – were more appropriate for a ten-year-old who wishes to take his ball home. Diarra’s booking, for an accumulation of petty fouls, was one of only two yellow cards shown to his side. By far the worst and most dangerous challenge of the game was that by Wayne Rooney on Niko Kranjcar in the first half.

Rooney did not deserve to end up on the losing team. When United were caught on the counter-attack in the 76th minute, the forward and Anderson were the players who were chasing back in pursuit of Kranjcar and Milan Baros. The Portsmouth duo had too much wit and when Tomasz Kuszczak – a half-time replacement for the injured Edwin van der Sar – pulled down Baros, a penalty and a red card were inevitable. Rooney, typically, wanted to go in goal, but Ferguson, venturing 15 yards on to the pitch, advised Rio Ferdinand to do so. Ferdinand guessed correctly, diving to his left, but Sulley Muntari’s kick was too powerful.

Even after that, with an extra man, Portsmouth were put under serious pressure, but they held firm. And they deserved to. While Ferguson furiously pointed to his watch, suggesting that there should have been more than four minutes of stoppage time, Redknapp celebrated joyously. Luck was on Portsmouth’s side, but they and their manager had more than deserved it.

How they rated

Manchester United
4-4-2

E van der Sar 5
W Brown 5
R Ferdinand 6
N Vidic 6
P Evra 7
C Ronaldo 6
O Hargreaves 5
P Scholes 5
Nani 6
W Rooney Y 6
C Tévez 5

Substitutes
T Kuszczak R 4 (for Van der Sar, 46min), M Carrick 6 (for Hargreaves, 60), Anderson 6 (for Tévez, 69). Not used: J O’Shea, Park Ji Sung.

Portsmouth
4-5-1

D James 7
G Johnson 8
S Campbell 8
S Distin 8
H Hreidarsson 7
J Utaka 5
L Diarra Y 8
P Bouba Diop Y 7
S Muntari 7
N Kranjcar 6
Kanu 4

Substitutes
M Baros 7 (for Kanu, 54min), Lauren (for Utaka, 74), R Hughes (for Kranjcar, 81). Not used: J Ashdown, A Mvuemba.

Referee M Atkinson

Attendance 75,463

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