Alex Ferguson admitted Nani could give him more selection headaches if he continues to put in displays of the kind that helped Manchester United to a 2-1 victory against Reading and a place in the FA Cup quarterfinals.

The Portuguese winger came off the bench in the first half to replace the injured Phil Jones and scored after the break before setting up Javier Hernandez for United's second goal, which proved crucial as Jobi McAnuff pulled one back for Reading.

"Nani's got great talent and I had a feeling he would win the game for us," Ferguson said.

"You could see he was right on form and he had two great strikes straight away and he was a threat to them the whole night.

"If he keeps that form up, it makes my job even more difficult," said the United boss, whose side faces QPR in the Premier League on Saturday as it looks to maintain its 12-point lead.

In the FA Cup, United will face the winner of Chelsea and Middlesbrough, who play each other in their delayed fifth-round tie, but Ferguson is unperturbed by which side makes it through as United has home advantage.

"We have a home tie and it can't get any better than that. You can't wish for anything more than that. No matter who we play, a home tie at Old Trafford means we have a great chance," Ferguson said.

"This was a Cup tie we got out of the road and now we have a big league game on Saturday at QPR and hopefully we can keep the momentum going."

Nani replaced Jones just before the break as the defender hobbled off with an ankle injury after a challenge from McAnuff.

"We will have to assess it," said the United manager. "It is an ankle injury so I would imagine he would not be ready for Saturday and we will see what he is like after that."

Nani opened the scoring in the 69th minute when Antonio Valencia found him in the area and the winger, who was involved in a car crash in Manchester last Friday but was unhurt, controlled with his left before rifling in with his right.

Adam Le Fondre had a shot saved by United keeper David De Gea moments later but almost immediately Nani sprinted clear down the right before crossing for Hernandez, who bowed down to nod in at the front post.

That looked to be the tie wrapped up but Reading battled back and started to bombard the United area before a mistake from Chris Smalling nine minutes from time allowed McAnuff in to shoot low past De Gea.

Le Fondre headed over in stoppage time as Reading threw everyone including goalkeeper Adam Federici forward but United held on.

Reading now returns its focus to Premier League safety and has a home game with fellow struggler Wigan on Saturday.

"We have been learning in the Premier League and we now have 12 games, the first against Wigan on Saturday at the Madesjki," said manager Brian McDermott.