So the abacus was not needed after all. Having caved in at Stamford Bridge in midweek, Derby were heavy odds-on to suffer similar humiliation when Manchester United came calling to a packed Pride Park. Instead, as hopes of a miracle result began to mount, there was only a quarter of an hour left when Ronaldo settled it.
The goal ensured United's continued assault on the Premier League title and Derby's unchecked plummet in which their only win came back in September. It was the 31st strike of the season for the incredible Portuguese, 22 of them in the League, and it was not too much of an exaggeration to say that he might have had another 22 yesterday, when he was frustrated time and again by the brilliance, and occasional good fortune, of Roy Carroll. The man who once stood between the posts at Old Trafford stood between his old team and a cricket score.
"We have to thank Ronaldo again for a fantastic goal," said his manager, Sir Alex Ferguson. Derby manager Paul Jewell's witty take on the match-winner was that "if [Ronaldo] was good looking he would probably have everything." For long spells he, and the rest of his team, had everything but a goal and it did not come until Ferguson had sent on Louis Saha and switched the previous spearhead duo of Wayne Rooney and Ronaldo to left and right sides respectively. Michael Carrick, who came on along with Saha in place of Paul Scholes, sent a ball inside Andy Todd for Rooney to chase, though even then there appeared no danger.
But Ronaldo's radar was alert to the possibilities and he accelerated into the penalty area as Rooney duly delivered a cross. It was not an easy one to cope with but, in mid air, Ronaldo managed to get over the ball and sidefoot a volley wide of Carroll, a feat which Ferguson paid full credit to.
A goal might have come in the opening seconds of a match contested in a drizzle and on a greasy surface. Again in the air, Ronaldo flicked a pass out to Ji Sung Park and was in the right place to meet the centre and start Carroll out on his busy afternoon. Another minute, and Ronaldo showed why United are riding high and Derby heading for relegation, taking a fine pass from Patrice Evra to accelerate past Marc Edworthy. It was Porsche against pushbike.
Ferguson signalled pleasure that, unlike in the Cup loss to Portsmouth, Ronaldo was not left unprotected by the referee. "Last week he felt frustrated about the fouls he suffered and I told him 'You do what you are good at, don't stop'." Against Derby he was brilliantly non-stop and Phil Dowd quickly had his yellow card out following clattering tackles by Darren Moore and David Jones. This served to curb Derby's excesses but not their enthusiasm. With their captain Robbie Savage hurtling around manically, Derby at first hung on as Ronaldo hit the post, then just missed the post and Ryan Giggs twice lifted inviting openings high.
Eventually their passion began to pay, or as Jewell put it, "We grew into the game." That growth, for a spell, was impressive for the home crowd and worrying for United. Ben Foster, making his debut in goal having joined United three years ago from Stoke for £1m, was finally able to show what a future he has at Old Trafford. First, he sprawled to his left to turn away Kenny Miller's volley and then, when Miller slipped clear of Nemanja Vidic for the only time, Foster again denied him superbly.
The second half was Ronaldo versus Carroll, a duel of free-kicks. The first, from 30 yards, struck Carroll on the chest as it skidded off the turf and from the corner he knew even less about the Ronaldo header which hit him on the line. Another free-kick from similar distance thundered a foot wide and when Ronaldo next closed in for a shot the travelling fans' celebrations were premature. The netting he rattled was the side net. It could not last, and it didn't. But Derby's brave battle made for an unexpectedly exciting contest.