The Ivory Coast international believes Pep Guardiola\'s reigning European champions are lacking confidence at the back but acknowledges Lionel Messi is the best player in the world.Salomon Kalou has revealed that Chelsea will target Barcelona’s defensive “weaknesses” in their mouth-watering Champions League semi-final.The revitalised forward believes the Premier League club can also take heart from the fact that the European champions are not top of La Liga.Kalou scored the crucial away goal for Chelsea as they defeated Benfica 3-1 on aggregate to reach their sixth Champions League semi-final in nine years.“Every team has its weaknesses,” said the Ivorian.“They have their weakness, we know that we can play on that. We know that they haven’t been so confident at the back, conceding a lot of goals so that is something we can play on.“Everyone forgets that [Real] Madrid are having a great season with Jose [Mourinho]. Right now, if we had played Madrid people would not talk that Chelsea has no chance because it’s Madrid. But because it’s Madrid, because they have [Lionel] Messi and all those players people are thinking that we can’t make it. The Chelsea players only know that this is one game and in one game everything can happen.“At the end of the day, we have to face them [Barcelona], you have to play, it’s a football game and every game is possible. I think they are one of the best teams right now with the best player in the world. But it doesn’t leave room for us to not believe that we can beat them.“Our fans expect us to win, we expect to win. People see the way Barcelona play today, they can say ‘Chelsea have no chance against Barcelona’ but, as a player for Chelsea, we work hard every day in training and we believe that on the pitch that is the only way of answering all those negative thoughts thinking that we can’t do anything.”Asked about Messi, Kalou added: “He is the best player in the world, no doubts. You can’t have any discussion about that. We hope that in the two games against us, he won’t be the best player.“I think this season was a difficult season for us. We are getting back together as a team, we are fighting as a team and I think that will be a great way of showing that Chelsea is still a good team.”But after Mourinho suggested that his former side stand no chance of beating the reigning champions, Kalou insists Chelsea will not pay any attention to his comments.“We can see Barcelona as a big competition of Chelsea,” the Ivorian observed.“Chelsea is coming back to its top level and Barcelona being the best team in the world for the past couple of years. The only way we can show that we can also be a great team is to go on the pitch, work hard and try to beat them.“We learn from the past. We know that if you give them the ball and give them the chance to play they will punish you. That’s a good thing to know. It’s still a difficult game but I still believe we can pull it through.”