FA Cup/Manchester United 2 Portsmouth 1:Wayne Rooney answered Manchester United's FA Cup SOS at Old Trafford as the Red Devils overcame two horrendous moments of ill-fortune to book a place in the fifth round at Portsmouth's expense.

Rooney was only introduced on the hour as United struggled to make the decisive breakthrough against their Barclays Premiership rivals.

But, having broken a seven-match drought at Arsenal last weekend, the 21-year-old followed up with a late double, the second a sensational chipped effort from 20 yards.

In contrast to his staggering second effort, Rooney's opener — his 10th of the campaign — was a tap-in, provided by Ryan Giggs.

It helped relieve the tension of a game which seemed destined to finish deadlocked, probably saving referee Mike Riley a hairdryer blast from Sir Alex Ferguson in the process.

On this ground almost two years to the day ago, while he was still at Tottenham, Pedro Mendes was on the wrong end of an abysmal call when none of the officials managed to spot Roy Carroll dropping the midfielder's shot a yard over his own line.

At the same end, just 12 minutes into an intriguing contest, Mendes finally gained some recompense, hooking a Nemanja Vidic header parried into his path by David James away from danger — despite the ball clearly crossing the line.

If that was not bad enough for the hosts, they also saw a perfectly good Henrik Larsson volley incorrectly ruled out for offside after half-time, a moment which must have left Ferguson wondering how many ladders he had walked under recently.

In the end though, Rooney's arrival ensured there was no need for recrimination, even if Mendes' late deflected effort meant United were not able to book their spot in the last 16 without some anxiety.