Guardiola said he expected, and got, a tough game against Chelsea and anticipated another one next week at the Nou Camp after the European champions were beaten on a rainy night in west London.
"A team does not reach the semi-finals of the competition six times in nine years without being a strong team," Guardiola said after seeing his side totally dominate Chelsea, but still end up losing to Didier Drogba's goal late in the first half.
Guardiola, whose side created 24 scoring chances of their own without finding the net, added: "I wasn't expecting to create so many chances. Nevertheless, we did, but we could not score and that was the issue.
"We knew it was going to be a challenge and it was going to be difficult but we will have to see what happens in the second leg. It is never easy coming to Stamford Bridge.
"But at home next week we will try and create as many chances but it is never easy against a team that defends so deep but we will try it."
Although his players were disappointed to have lost for only the third time in 63 matches this season, Guardiola said matters could be very different in the return leg.
"It doesn't matter how we feel now. Our focus and our target is to win the Champions League again and it will be a different match. It will be tough, but we are focused."
In a sense, Wednesday's result was a form of revenge for Chelsea's interim boss Di Matteo. Twelve years ago to the day, Guardiola was in the Barcelona side that beat a Chelsea side containing Di Matteo 5-1 in a Champions League quarter-final, but the Italian was more concerned with the events of Wednesday and next week rather than the past.
"I watched them against AC Milan and against Real Madrid, "he said, "and they did exactly the same. They have a unique style of playing and with quality players that's what they do to you.
"The balance has to be good within your own team to beat them. You need to be able to close down the spaces as much as possible and limit the threat as much as possible... it was not just the defence it was a defensive team effort tonight."
Drogba's goal was Chelsea's only shot on target but Di Matteo added: "I think that when you score a goal and win the game you deserve to win. Certainly they had more possession and a few more chances but they always do so. You have to be clinical when you play Barca and take any chances you get."
Looking ahead to the second leg, he said: "I don't think it makes us favourites. You know what to expect when you play at the Nou Camp. It's going to be very, very difficult but we have to believe we will score a goal there. We have to be at our best there."