The previous five teams to defend the Champions League trophy have not fared well in the attempt and last night Manchester United discovered why. The monumental effort of winning the thing, coupled with defending it and maintaining an assault on the domestic title, is gruelling beyond belief, even for a collective of the world’s finest players. In the past four seasons, AC Milan, Barcelona, Liverpool and Porto did not make it beyond the knockout round of 16 as champions of Europe; five years ago, Milan were knocked out in the quarter-finals.

With Cristiano Ronaldo involved from the substitutes’ bench for the first time this season, the match represented a final chance for the rest of United’s squad to prove that they are a vital force without him and the opportunity was missed. United looked tired, again. Perhaps this was the result of having too many players — Gary Neville, Nani and Owen Hargreaves — coming back from injury. Maybe it is the hangover of a season that ended in the small hours in Moscow in May in a finale that would have left them drained, physically and emotionally.

It could simply have been the lack of wit in midfield, with Paul Scholes and Michael Carrick absent. Either way, something is missing from United and Sir Alex Ferguson, the manager, must hope that it is only Ronaldo, and not a deeper malaise.

United will not press the panic button after a single draw in a group schedule of six matches, nor should they. There is plenty of time to make amends and two teams qualify, but a side picked with one eye on the match away to Chelsea at the weekend demonstrates the demands on the Barclays Premier League elite. As well as the ring-rusty inclusions, key players were rested because Ferguson thought that he had enough to beat Villarreal, but the Spanish team proved surprisingly resilient.

They were the last side to get a result in the Champions League at Old Trafford — in the 2005-06 season when United failed to get out of the group, for those who believe in doomy portents — and defended with spirit, even if little was threatened. Ronaldo arrived in the 61st minute, but even he could not break them down, although United looked a different team once he was on the pitch.

His reception was a pre-match talking point, but there was no hint of resentment from Old Trafford loyalists, despite dire warnings that the player would never be accepted as a true Red again after his summer dalliance with Real Madrid. Fans are a pragmatic lot.

By the time Ronaldo was introduced for Park Ji Sung, the match was drifting to such an extent that he could have warmed up in a Real tracksuit and still got roars of encouragement. Faced with a stalemate, the supporters saw not a traitor, but a guy who could win a match that was heading for a draw. Ronaldo got the biggest cheer of the night, and did his utmost to justify it.

Chelsea will not have enjoyed this first glimpse of last season’s Footballer of the Year. Far from looking a player who had missed pre-season and not kicked a ball since June, Ronaldo was an inspiration and had a big say in the two chances that could have earned United a late winner.

He looked as if he had never been away, in fact, switching flanks, always available, ever on the lookout for mischief. In the 71st minute, it was his fine pass to Wayne Rooney that put the England striker away before he crossed to Carlos Tévez at the far post. The Argentina forward shot sharply, but Diego López, the Villarreal goalkeeper, got just enough on the ball to slow it a fraction, enabling González Rodríguez, the right back, to clear on the line.

In the 82nd minute, a cross by Ronaldo from the right was met by Jonny Evans, the defender spurning the chance to be the hero of the night with a diving header that struck a post. He will play against Chelsea in place of the suspended Nemanja Vidic, though, and justified his inclusion with a solid performance.

Perhaps it might have been different had Rio Ferdinand, Evans’s centraldefensive partner, not spurned the chance of the night after eight minutes. Had United scored early, Villarreal’s ordered plan might have collapsed and the champions of Europe might have stormed through as easily as Chelsea did against Bordeaux on Tuesday. Instead, Ferdinand — the one player exempt from criticism by Ferguson after Saturday’s defeat by Liverpool at Anfield — flapped when the ball from a corner by Hargreaves fell at his feet and shot wide. United also had a strong penalty appeal for a foul on Park turned down.

Villarreal were dogged, but it was clear that United were not going to be troubled much in defence and the occasional intervention from the ageing Robert Pires aside — up against Neville on the flank, it reminded of one of those veterans’ games, a blast from the past from two players who enjoyed fantastic battles in the days when Arsenal and United appeared to contest every title — Villarreal barely threatened.

It was a surprise when, in the 59th minute, the visiting team struck a post through Guille Franco, the striker, after one of the night’s best passing sequences. It ended with a cross whipped in by Ángel López that Franco met with an intricate back-heel flick. The ball struck the inside of a post with Edwin van der Sar beaten. Needing no further warning, Ferguson brought on Ronaldo.

Later, the United manager expressed his satisfaction with the performance — a contrast to Luiz Felipe Scolari, of Chelsea, who was angry at his players after a 4-0 win the previous evening — but he will know that this should have been three points for United. That has been the dividend from the first home Champions League match over the previous nine seasons. Ferguson will hope that it is not another omen for the champions of Europe.

Manchester United (4-4-2): E van der Sar — G Neville, R Ferdinand, J Evans, P Evra — Park Ji Sung (sub: C Ronaldo, 61min), O Hargreaves (sub: Anderson, 61), D Fletcher, Nani — W Rooney, C Tévez (sub: R Giggs, 80). Substitutes not used: B Foster, W Brown, Anderson, N Vidic, J O’Shea. Booked: Tévez.

Villarreal (4-4-1-1): D López — Á López, G Rodríguez, D Godin, J Capdevila — Cani (sub: S Cazorla, 46), Edmilson, S Eguren, R Pires (sub: A Ibagaza, 66) — M Fernández, G Franco (sub: J Llorente, 76). Substitutes not used: S Viera, J Venta, M Senna, F Fuentes. Booked: Franco, D López, Ibagaza.

Referee: W Stark (Germany).