If Chelsea are to become the first club in the Champions League era to win back-to-back titles, they are going to have to eliminate the mistakes that cost them victory in their 2-2 draw with Juventus on Wednesday.
The Italian champions handed them a reality check at Stamford Bridge as Chelsea began their quest to emulate Franco Baresi's AC Milan side that boasted the Dutch trio of Ruud Gullit, Marco van Basten and Frank Rijkaard and were the last to lift successive European Cups in 1989 and 1990.
That trophy was paraded around Stamford Bridge before the opening Group E match against Juve, but if Chelsea are to retain their glittering prize, they cannot let teams escape as Juventus did.
Coach Roberto Di Matteo said before the game they would not underestimate Juve, back in the competition after a two-year absence and coming to London after going unbeaten for 42 games in Serie A.
"So far, it's been impossible for anyone to win it twice, so we will try to do the impossible," Di Matteo said on Tuesday.
After his side established a 2-0 lead with both goals coming from Brazilian debutant Oscar, di Matteo watched on helplessly as Juve fought back to draw with Arturo Vidal scoring before half-time and substitute Fabio Quagliarella grabbing the equaliser in the 80th minute.
Chelsea weathered all kinds of crises during last season's roller-coaster Champions League campaign to become European champions for the first time when they beat Bayern Munich on penalties in Munich in May.
At times it seemed as though a divine hand was guiding Chelsea towards Europe's greatest club prize, but already twice this season in Europe they have looked far more mortal.
Three weeks ago they were outplayed 4-1 by last season's Europa League winners Atletico Madrid in the European Super Cup final in Monaco after they gave an unimpressive, listless display.
That defeat in a one-off season curtain-raiser was relatively inconsequential, but dropping two points at home at the start of this season's Champions League campaign could have longer term repercussions.
Last season, especially at home, Chelsea were invincible, winning all six Champions League matches at Stamford Bridge, but that run ended when John Obi Mikel's mistake in the 80th minute created the equalising opportunity Juventus grabbed with relish.
Mikel apologised afterwards saying: "If I want to make up an excuse, I can, but for me, I gave the ball away.
"I put my hands up, we move on. I'm sorry about the mistake, but there are no excuses. I think that's what you get from playing in the Champions League. You make a mistake, you get punished for it.
"I think we looked so good all throughout the game, except when it was 2-2. We just lost our head."
Di Matteo said he was disappointed and deflated by the result, but it was not all bad news for the holders.
Oscar, on his full debut scored twice in three minutes in the first half. Both were long range efforts, the second a contender for Champions League goal of the season, and overall Chelsea played well and Di Matteo's gamble on starting with Oscar paid off.
Juventus though, were no pushovers and although they have been out of the elite competition for two years, they have a greater European pedigree than Chelsea and served warning they too could be in contention in the latter stages.
Their assistant coach Massimo Carrera said afterwards: "We went two down but we never stopped fighting. That shows the character of Juve, we have a spirit that never weakens.
"We made a few mistakes and need to work on them. We could have won, we could have lost and we drew and proved that we could play European competition at this level. I'm happy with the result."comments