Never does it in the big matches, does he? Never does it when the pressure is on against the best teams. Never scores the ones that matter.

So, how to explain this and satisfy those who still doubt? Noted small-game player Cristiano Ronaldo set Manchester United on the way to an entirely meaningless Champions League semi-final with a not-at-all brave header against the completely useless second-best team in Italy in the benign atmosphere of the dilapidated cowshed that is the Olympic Stadium. There, that should please them.

The reality is different, however. Wayne Rooney’s second-half goal may have settled the game, and surely the tie barring a catastrophe in the second leg at Old Trafford, but it was Ronaldo who was the hero of the night, the man whose courage and willingness to put his head where most jinky wingers would not put a foot sets him apart from all contemporaries, certainly this season.

Players with Ronaldo’s skill are not meant to score headers. Certainly, they are not meant to score the type of header most commonly associated with the towering lumps of gristle who play at centre half. That is what he did last night. Ronaldo scored the sort of headed goal that John Terry used to get for Chelsea, before he was marked to anonymity at corners; the type that makes everybody in the arena flinch, that ruins smiles and distorts cheekbones.

Ronaldo’s determination to get on the end of the ball in the 39th minute came close to demonstrating a streak of madness. At the very least it presented a serious challenge to his status as a poster boy: not unless he fancies a career endorsing dental cement.

That is what makes him special and what made his 36th goal of a remarkable season special, too. When Rooney over-hit a pass to Paul Scholes that was chased down and lobbed back into the penalty area, there was something almost demonically possessed about the way Ronaldo hared into the space and launched himself at the floating ball. A player needs to keep his eyes open to direct a header in that instance, he needs to be prepared for any foreign object to meet his face — head, elbow, boot, shoulder, the fist of an advancing goalkeeper.

Ronaldo was knocked to the floor by the upper torso of David Pizarro, but as he fell he could no doubt see the ball pitching wide of the outstretched hand of Doni, the Roma goalkeeper. It will have made the fleeting pain worthwhile.

As will the victory for which his goal laid the foundation. Roma were always vulnerable on the counter-attack after that and, pushing desperately for an equaliser in the second half, Rooney delivered what should prove the decisive blow. Roma had been enjoying their best spell of the game when Wes Brown launched a deep ball from the right. It looked to be a lost cause but was chased down by Park Ji Sung and when he nodded it back, Doni made a hash of a simple catch and the ball dropped to Rooney, who bundled it into the net.

The light left Roma after that. The remaining chances fell to United, a shot by Michael Carrick that flew wide after 71 minutes, another effort from Ronaldo set up by Carlos Tévez and spurned.

There were five Englishmen in the starting line-up. That doesn’t happen often, either.

It certainly makes the return leg less problematic. Even if Francesco Totti and Juan return for Roma, there is no reason why United should fear a team who have now defeated them only once in five matches over the past year.

Nor is great exertion needed. It would be nice to see the level of performance that produced last season’s 7-1 win, but nobody would blame United for choosing to manage the game instead, with so many important ones coming up over the next month. They will not want to take risks with injuries, either.

The biggest disappointment of last night’s match was the knee injury to Nemanja Vidic, who has been such a rock at the back beside Rio Ferdinand this season. After a scare immediately after Vidic had left the field, Ferdinand recovered to turn in a fine game.

John O’Shea did well as a replacement, but even so, if Vidic’s absence is a matter of weeks rather than days, it will be a blow. He landed awkwardly after challenging for a header with Mirko Vucinic, the Roma striker, and twisted joints from that height are rarely uncomplicated. Sure enough, when Vidic departed in the 32nd minute, Roma put United under pressure and the patched-up back four did well to weather the storm.

In particular, the experienced presence of Edwin van der Sar, the United goalkeeper, proved invaluable. Roma’s introduction of Ludovic Giuly after 59 minutes had an immediate impact and the Dutchman thought quickly to throw himself on to his dangerous low cross, Giuly’s first touch of the game. Just two minutes later, Van der Sar was in excellent nick again, palming out a header from Vucinic one-handed.

On other occasions, Roma had only themselves to blame. Vucinic skipped around Ferdinand before finishing the wrong side of the far post, while Max Tonetto, the right back, put another chance wide and Christian Panucci, the defender, missed a peach after Mancini had headed on a long throw, volleying over from less than six yards with the goal gaping. He fluffed a header in the first half, too. Maybe he was saving his best for a big game.

AS Roma (4-2-3-1): Doni – M Cassetti, P Mexes, C Panucci, M Tonetto (sub: Cicinho, 69min) – D De Rossi, D Pizarro – Taddei (sub: L Giuly, 59), A Aquilani (sub: M Esposito, 76), Mancini – M Vucinic. Substitutes not used: G Curci, Antunes, M Ferrari, M Brighi. Booked: Pizarro, Mexes.

Manchester United (4-5-1): E van der Sar – W Brown, R Ferdinand, N Vidic (sub: J O’Shea, 32), P Evra – Park Ji Sung, P Scholes, M Carrick, Anderson (sub: O Hargreaves, 55), W Rooney (sub: C Tévez, 83)– C Ronaldo. Substitutes not used: T Kusczak, R Giggs, G Piqué, M Silvestre. Booked: Anderson.

Referee: F de Bleeckere (Belgium).