CRISTIANO Ronaldo proved that persistence is a virtue as he scored his 31st goal of an astonishing season to spare Manchester United from potential embarrassment at rock-bottom Derby.

With his ninth off 11 chances overall in the game, and in the 76th minute, Ronaldo finally broke brave Derby's resistence by scoring the only goal to keep United firmly in the hunt for back-to-back titles.

It was cruel on doomed Derby in one respect, but deserved by the Reds in another, stretching the Rams' winless streak in the Barclays Premier League to 24 matches.

It was unsurprisingly men against boys, yet somehow Derby headed into the interval on the back of the most incredulous scoreline of their wretched season as they had held United scoreless.

For the opening 20 minutes the rout everyone had expected was on the cards as United carved up the Rams at will, and it appeared only a matter of time before they would make the breakthrough.

Yet it never came, and as the half wore on, Derby steadily grew in confidence and towards the end of the period they even had the audacity to create two gilt-edged openings of their own.

Mauled

As far as Sir Alex Ferguson was concerned, that was not in the script as a Derby side without a league win since mid-September should have been their for the taking.

After being mauled 6-1 by Chelsea at Stamford Bridge in midweek, Ferguson would surely have expected his side to hand out more of the same punishment to Jewell's beleaguered side at Pride Park.

The intent was certainly there, instigated after just 70 seconds as Wayne Rooney and Ji-Sung Park combined for the latter to whip in a cross from the right wing.

Ryan Giggs, returning as captain after missing last week's 1-0 FA Cup loss to Portsmouth at Old Trafford with a calf injury, should have done better with a downward header, but only succeeded in finding the arms of the outstanding Roy Carroll.

It was the precursor to a flurry of chances as Ronaldo curled a left-foot shot narrowly wide with only Carroll to beat following a through ball from Patrice Evra.

Giggs then drilled a drive wide after again being picked out by Park from the right, followed swiftly by Ronaldo striking the base of the right-hand post with a low, curling shot from 15 yards.

Surely the goal would arrive, but no, with Giggs again the culprit in the 19th minute as he sliced a shot wide after being set free by Rooney and Ronaldo.

The Portuguese star, who had been on the receiving end of a late challenge and a shirt tug from Darren Moore and David Jones that had earned bookings for the pair, was again a whisker away just after the half-hour.

But despite curling towards the top right-hand corner a superb shot with the outside of his right foot, Carroll was equally as superb with his save as he clawed the ball away.

Stunning

When the storm abated, Derby dared to take the lead themselves, only for debutant goalkeeper Ben Foster to underline his emerging talent with two stunning saves.

His first was a reaction stop as he turned aside a snap shot from Mile Sterjovski in the heart of the area, with his second moments later a fingertip stop in pushing away a low curler from Kenny Miller.

United ended the half with a Rooney drive into the sidenetting and a shot across the face of goal from Ronaldo, but it was Derby who left the pitch to a rousing reception from their fans.

After the break, it was Ronaldo who had all the chances, two from long-distance free-kicks early on that swerved viciously.

The first was superbly parried by Carroll, who proceeded to save a point-blank header from the ensuing inswinging Giggs corner, while the second was inches past the post.

A drive into the sidenetting then followed in the 71st minute at a stage when Derby were beginning to believe they could conjure an astonishing draw as they were battling manfully.

But in the end there was to be no stopping Ronaldo as he finally found the net with a 12-yard sidefoot finish to a Rooney centre after he had raced onto a looping through ball from substitute Darren Fletcher, on just two minutes earlier.

The game ended with two further opportunities for Ronaldo, but Carroll was equal to both, the culmination of a stirring battle between the game's two main protagonists.