Manchester United's pulsating 2-2 draw with free-running Porto on Tuesday was everything the Champions League aspires to, though United manager Alex Ferguson will wish it had been a more typical first-leg clash.
Porto deserve enormous credit for going to Old Trafford with a real willingness to attack and they should really have won the match such was their dominance in the first half.
Even after Carlos Tevez had put United ahead five minutes from the end, Porto still refused to sit back and hope their solitary away goal would prove key.
Instead, they poured forward to grab the equaliser through substitute Mariano, and that was the least they deserved.
United now travel to Portugal on April 15 probably needing to win, something no English team has managed in 12 previous attempts, though a high-scoring draw would also be enough to send them through.
"You have to think the last goal was one we could not afford to lose," said Ferguson.
"It was a terrible goal to give away when you are 2-1 up and seeing the game out."
United, who have looked rocky at the back in recent weeks as they lost successive league games to Liverpool and Fulham and needed a stoppage-time goal to beat Aston Villa 3-2, were again all at sea in the absence of the injured Rio Ferdinand.
Johnny Evans, who has generally been an impressive stand-in at centre back for much of the season, had a night to forget and will be relieved that his catalogue of errors did not lead to more Porto goals.
United's midfield were ineffective for long spells, producing little in attack and looking ragged in preventing Porto's counter-attacks from ripping through the home side's deep-lying defence.
It was all the more surprising coming only a few weeks after they were breaking records for consecutive clean sheets with Ferdinand and Nemanja Vidic being compared favourably with the great Old Trafford centre-back partnerships.
Goalkeeper Edwin van der Sar certainly earned his money on Tuesday, especially in the fiery opening half-hour when Porto scored through Cristian Rodriguez and could easily have had three more.
For all the problems, however, Ferguson will take heart from the steel shown by the likes of substitutes Tevez and Wayne Rooney, whose 15th-minute equaliser came after he showed a striker's instinct to gamble on Bruno Alves's back-pass, then great technique to turn the gift into a goal.
Ferguson said he was delighted to reach half-time level and, despite the late equaliser to make it 2-2, he recognised it was the least the Portuguese giants deserved.
The result, and the performance, persuaded bookmakers to lengthen the odds on United retaining their European crown, with Barcelona installed as new favourites.
Porto's home record is formidable but will they will risk a repeat of such a high-energy assault on the holders in the home leg when a 0-0 or 1-1 draw would send them through?
That dilemma is a chink in the armour that United will work on and Ferguson, never more effective than when his back is against the wall, will relish the chance to claim another European landmark.