Chelsea goalkeeper Petr Cech and defender David Luiz felt the early goal conceded by the Blues helped Shakhtar Donetsk settle down and take full advantage as the home side eventually sealed a 2-0 victory in their Champions League game Tuesday.
Chelsea now have a tough job on their hands to ensure qualification to the knockout rounds, with Shakhtar taking control of the group, which also included Juventus and FC Nordsjaelland.
"I wouldn't say it was a shock if you knew this was a pure, counter-attacking team and we allowed them to score in the third minute," Cech said. "This had a huge impact in the game because when we had possession and lost it they had the chance to counter, to shoot, to finish.
"They have been doing really well and we gave them a huge lift in the third minute, then we saw them play with the confidence.
"We started slowly the same as (in the second half) against Tottenham (on Saturday) and we got punished for that. We have to make sure we start games better than this."
"The early goal gave them big confidence," Luiz added. "When you score in the first five minutes in your own stadium you have a lot of support.
"It was a difficult game and we didn't play well. When you play for a big club you need to be a big player when you lose and we saw the truth of the game, we should have played better and didn't give ourselves the opportunity to win the game.
"It was a hard game, everybody who saw it knows that. We have to say congratulations to Shakhtar because they played well."
Chelsea have been far from convincing in their defense of the Champions League title this year, but the Blues were handed a reprieve of sorts after Italian champions Juve failed to take advantage of the slip-up only managing a 1-1 draw against Nordsjaelland.
"Obviously 1-1 there is a result which suits us because we dropped points here and we still play them, so we are still ahead," Cech said. "Let's forget about this one, we have a massive game at the weekend, a replay at home and hopefully it will be a different story."
That massive game will see Manchester United look to end the near-perfect record of Chelsea in the English Premier League, and Cech believes the Blues have to learn from the mistakes made in the Shakhtar game. "In a way what happened today was a good experience for us because we have to defend better," Cech added. "We played well when we have the ball but not when we didn't have it.
"If you do this against Man United you are in big danger because they are the same type of team. Hopefully it was a good lesson and we learn for the weekend."