The Blaugrana were punished for their profligacy by the Blues, who will take a one-goal advantage to Catalunya thanks to Didier Drogba's first-half strike
The Blaugrana bossed the game in west London from start to finish but paid the price for failing to turn their dominance into goals and were rocked by a sucker punch from Didier Drogba just before the break.
As a consequence, Barca's hopes of retaining its Champions League crown are now hanging in the balance, but Valdes, who was playing in his 100th game in Europe, still believes the Catalans will make it to Munich.
"We are confident that we can overturn this deficit," the goalkeeper told reporters after the game. "We generated many goal chances and we shouldn't forget that.
"We will have our fair share of chances in the return leg and I think we will make the most out of them, no matter what."
Valdes' teammate Pedro, who hit the post late on, was just as bullish when he faced the press shortly after the full-time whistle at Stamford Bridge.
"We were better and it's a shame we couldn't win," the winger lamented. "But I'm very confident that we will be able to overturn it.
"However, we feel terrible because we played a great match and we had this bad result. We looked like fools when they scored because we were clearly dominating."
The return leg takes place at Camp Nou on Tuesday evening, though Barca's attention now diverts back to La Liga and Saturday's crunch Clasico clash with leader Real Madrid.