Brendan Rodgers believes Barcelona's Luis Suarez is the biggest threat his Celtic side will face on Tuesday night, calling the forward the best player in the world.
Rodgers worked with the 29-year-old at Liverpool and paid tribute to the Uruguayan's personality as well as his ability.
"First of all, when you speak about Luis Suarez, you have to speak about the man," said Rodgers.
"Luis Suarez is one of the most beautiful men you could come across. He's a very humble guy who works tirelessly at his profession. He is a super-professional, a family man who gives everything for his life as a footballer and his family.
"I had the pleasure of working with him for two years and he was incredible and as a footballer, he is the best in the world.
"The biggest compliment you can give Luis is that he came to an already world-class team and he made them even better."
Celtic face Barcelona at the Nou Camp in their opening game of Champions League Group C on Tuesday and Rodgers admits that Suarez could prove unstoppable.
"When I see them play now, Barcelona would not be the same team without Luis Suarez.
"Like all world-class players, they always find a space. You can have tactical ideas, you can park two double-decker buses in front of the goal, but I think that sometimes the best players in the world will always find a space.
"You have to try and do as much as you can to negate that and be as aggressive as you can in order to stop them and that is something we hope we will do but he is the best striker in the world at this moment in time, I don't think there is any question in that.
Celtic defeated Rangers 5-1 on Saturday and when asked whether Barcelona was a "free game" of sorts for the Hoops, Rodgers rejected such claims.
"For me, it's not. We are here to look to get a result. We understand and respect the difficulties there is to get a result here, coming off the back of the intensity of the programme we have been on and the Rangers game at the weekend and everything that we put into it to get the result.
"We respect this is arguably the best team in the world with probably a front three that is maybe the best of all time.
"I know working with Luis that Luis on his own could occupy a back-four defence. So if you add Neymar and Messi into that then of course it is a very difficult task, but as a manager you have to believe you can get a positive result.
"We want to come and enjoy it but we want to come and get a result. We are not here just to be passengers.
"If you want that easy life, it is not the level to be playing at."
Barcelona go into the fixture off the back of a shock 2-1 defeat at home to newly-promoted Alaves.