Victor Wanyama believes Celtic are capable of defeating Barcelona for the second successive year in the Champions League group stages.
The Kenyan midfielder, who left the club to join Southampton this summer, scored a header and produced a man-of-the-match display as Neil Lennon’s men secured a famous 2-1 victory over the Catalan giants in Glasgow last year.
Wanyama has been watching Celtic closely since making his move down south and is optimistic they can secure another upset, particularly with Lionel Messi out injured.
"I believe Celtic can beat them again - they just need to take their chances," he said in his column for The Daily Mail.
"It is a game with a lot of good memories for me. When I scored for Celtic and we beat them 2-1 last year it was one of the highlights of my career.
"To play well, to score and to beat as big a team as Barcelona was incredible.
"Javier Mascherano is injured and Lionel Messi got injured on Saturday so maybe Celtic can take advantage."
The midfielder believes strong concentration and work rate will be pivotal to stand a chance of beating the Spanish champions on Tuesday and says matching a side of that quality for 90 minutes is a real mental test.
Wanyama said: "I knew we had to be very strong in the middle of the park as that is their strongest point. It's not just with Iniesta and Xavi but Busquets and Fabregas too.
"They keep the ball so well and work to press it too. They can hurt you - it isn't easy. We needed to concentrate 100 per cent because the second you go to sleep they can kill you off.
"We had to be focused all the way through. Afterwards when you play them you are not just tired physically but mentally. Your head hurts.
"It's so important to try and stay strong - I just hope Celtic can do it again."
Wanyama admitted he was a frustrated viewer when Celtic went down 2-0 to AC Milan at San Siro in their opening Champions League encounter despite having had the better during lengthy spells of the match.
The 22-year-old added: "It was frustrating. It was such a good team performance. They were better than them all over the park. I just felt that if they had got one goal then they would have gone on to win by three or four.
"It's what happens at this level. They were so unlucky but Celtic found last year that there is greater importance in taking your chances because the top European teams often have a player that maybe does little else but finish."