By ESPNSTAR.com staff
The La Liga giants, who had won all of their games in the competition this season prior to their visit to Celtic Park, were expected to comfortably see off their Scottish opponents on Wednesday.
However, Victor Wanyama handed the hosts a surprise lead in the 21st minute, before 18-year-old Tony Watt all but sealed the win seven minutes from time in his Champions League debut.
Lionel Messi pulled one back for Barca in injury-time but it proved to be too little too late as they succumbed to only their second defeat of the season in all competition, but Vilanova was quick to defend his players after the final whistle.
"There is nothing to blame the players for," he said on UEFA's official website. "On the contrary, we must congratulate their effort to read the game properly from the beginning.
"I think we deserved to win - we tried everything until the end. We made a mistake at a set-piece and they seized their opportunity. We only conceded two corners and they scored from one of them."
"We read the game well, we created a lot of chances but we weren't on target and their keeper was brilliant," Vilanova said.
"We did what we needed to do in these types of games, we've seen this on other occasions. This is the type of football that the Barca fans want to see. Besides, I prefer to have an enjoyable time watching the team from the bench.
"I'm pleased because they gave it their all until the end."
While the 43-year-old did admit his side wasted a good chance to open the scoring shortly before Celtic did so themselves, he was effusive in his praise of their conquerors, who celebrated their 125th anniversary a day before.
"Before their first goal we had a clear chance to score," Vilanova added. "I think the game would have been very different [if we had done so].
"I think we had enough chances to win the match. If there are many games like this, we will win the majority but that was not the case today [Wednesday].
"We must also congratulate Celtic for their good game, for winning and for their spectacular support. The atmosphere in the stadium was spectacular.
"We must congratulate them for their 125 years and hopefully many more to follow."
"We're still in first place in the group, we're not worried," he said. "I think we did a good job, we created chances but the ball didn't go in.
"The same thing happened at the Camp Nou. They played defensively and they waited to make fast counter attacks. They are very comfortable on corners and set pieces, and that's how they scored their two goals."
Jordi Alba was equally pragmatic about the result and believes he is beginning to settle into the side following his summer transfer from Valencia.
"If we hadn't had the chances we created I wouldn't be leaving with the feeling I have, but it's time to focus on our next match," he said.
"We're coming up against teams that close themselves off at the back and we're finding it difficult to get into the opposing team's area, but we're not worried about it.
"The match allowed for the right and left-backs to push forward. Each day I'm feeling better and more comfortable when I go forward.
"They created chances on set pieces because they know we're not a very tall team, but we also created a lot of chances but their keeper was brilliant."
Barca will be looking to get back to winning ways on Sunday when they visit Real Mallorca in the league.