Iaquinta had been on the pitch just seconds when he scored with his first touch of the game in the 76th minute.

Earlier a Mauro Camoranesi bullet header had levelled matters on the hour mark after Andrea Dossena had put the home side in front with just six minutes played.

The defeat makes it one point in four games now for Udinese, and continues their unlucky run against the big sides in recent weeks.

Back in January, Pasquale Marino's men kept European champions AC Milan at bay for 90 minutes until an injury-time goal robbed them of any points from the game.

The Udine outfit will again be disappointed not to have got something out of the game on Sunday after enjoying the lion's share of the chances but being frustrated time and again by the fit-again Gianluigi Buffon.

Udinese came out determined to get on top early on, and as a result had the ball in the net with their first chance of the game.

Buoyed by his goal for Italy in midweek, Fabio Quagliarella made a good run into the penalty area down the left and, when his shot was parried at the near post by Buffon, Dossena was on hand to tap home the rebound from close range.

Rather than sitting back and defending their advantage, Udinese continued to come forward in search of a second goal.

They nearly got it after 25 minutes when Antonio Di Natale got away from Giorgio Chiellini to find himself one on one with Buffon, but the Italy number one was more than equal to the shot to turn it away for a corner.

In the second half, the goalmouth action dwindled as Juve tried to keep hold of the ball and wait patiently for their chance.

It finally came on 60 minutes when Camoranesi rose the highest to meet an outswinging corner from the right and send an unstoppable header past Samir Handanovic and high into the net.

Di Natale had a shot from distance that failed to trouble Buffon before Alessandro Del Piero had the home fans worried when he went down in the penalty area but the referee waved his protests away.

But the goal Udinese fans were dreading did come in the closing stages.

With 15 minutes left, Claudio Ranieri replaced David Trezeguet with Iaquinta, and within 60 seconds of his arrival the man who once delighted the Fruili faithful silenced them with Juve's winner.

Pavel Nedved played a great through-ball through the centre of the home defence and Iaquinta made no mistake with the finish from the edge of the area.

There was still time for Gokhan Inler to bring a great save out of Buffon with a 30-yard effort and for a Di Natale chance that went high over the bar late on.

But the visitors hung on for the win which keeps them within reach of second-placed Roma.