Celtic's manager, Neil Lennon, reflected on one of the finest moments of his life after presiding over a famous defeat of Barcelona. Scotland's champions secured a 2-1 win over the team widely regarded as one of the greatest ever in world football. Celtic are now on the brink of qualification from Group G, with their victory only the second time Barça have lost in any competition since April.

"This is up there with anything I have done in my life," Lennon said. "As a player I won things, had a special 10 years under Martin O'Neill [at Leicester and Celtic] and played in some great teams, beating Manchester United and getting to the last 16 of the Champions League. As a manager, I don't know if I will top this; I hope I do, because I am still young and am still learning. But this is up there with anything I have achieved, not just in my football career but in my life."

Lennon praised his team, who had been rendered even bigger pre-match underdogs because of a batch of injuries. Celtic's triumph, which arrived courtesy of goals from Victor Wanyama and Tony Watt, came one day after the club celebrated 125 years since their inception. Lionel Messi scored an injury-time goal for Barcelona.

"This was one of the greatest nights in the club's recent history," Lennon added. "It was very poignant, firstly to be playing Barcelona at this point but also to beat them given the way our squad had been decimated.

"The players are heroes to me. I cannot speak highly enough of their performance. They will go down in the history books as the team which beat probably the best team in the world. When we scored first we knew we would need a bit of luck, and we got that. You need your goalkeeper to be fantastic to beat Barcelona. They will feel very unlucky to have lost – they hit the bar and the post – but the difference is Tito [Vilanova, Barça's manager] can bring on Cesc Fábregas and David Villa as substitutes. I threw on Tony Watt, an 18-year-old kid who cost £50,000 from Airdrie.

"I had no hesitation in playing him, I just thought his lack of experience would have been too much to put him in the starting lineup, but everything we asked him to do, he did. He scored a brilliant goal and should have had a penalty and a sending-off when he got on [Javier] Mascherano's wrong side. He is learning. He wrote himself into the history books of the club but he is 11 games into his career. Everyone goes on about tactics but football is about players and they have covered themselves in glory tonight."

Watt looked stunned when speaking in the immediate aftermath of his winner. "It'll take a couple of hours to sink in. I just saw Victor Valdés, I thought to put it to the side of him and it might go in. It's probably the best moment of my life – I'll look back at it when I'm older and think: 'We've just beaten Barcelona in the Champions League.' There's nothing better."

Wanyama, likewise, reflected on an "unbelievable" achievement.

Celtic's remaining matches are away to Benfica and at home to Spartak Moscow. It is four years since the Hoops last played in the Champions League's knockout phase. "Coming into the tournament we wanted to gain respect for the players, for the club and obviously for Scottish football as well," Lennon said. "I hope we have given the game here a huge boost. It has been in a bit of a lull but we have a great club here."

Vilanova praised Celtic's display but did not appear overly upset by a rare defeat. Barça remain at the top of Group G. "I would like to offer my congratulations to Celtic and their fans, who have been amazing tonight," he said.

"Before we played we knew Celtic were good at set pieces; we didn't want to concede many of them. They scored first and could defend even more but this is not the first game we have lost like this and it won't be the last. Their goalkeeper was fantastic and we missed a few chances.

"This was an important game but we still have two matches left to qualify."

Vilanova disputed the notion he should add some more physical attackers to his side. "Yes, we could sign some taller players, but I like to have fun on the bench as well. This is the way we play."