Arsenal manager Arsene Wenger believes that Barcelona are weaker than in previous season but thinks they, Real Madrid and Atletico Madrid are among the biggest threats in the Champions League this season.
The Gunners get their European campaign back underway with a home tie against holders Bayern Munich on Wednesday at the same time as Atletico face AC Milan and a day after Barca visit Manchester City, with the Blancos meeting Schalke a week later.
The Frenchman does not think the Catalans are as dominant as they were a couple of years ago but suggested they can still conquer the continent this season under Gerardo Martino.
"If I really thought about whether Barca are dominating in Europe as they did in recent years, I would say no," he wrote in his Eurosport blog. "But if you asked me if they can still win the Champions League, I would say so.
"I really want to see their tie with City because I love the way Barca play. They're still a team with great offensive strength but they will have to be strong in defence to stop from conceding goals at City."
Wenger thinks that Carlo Ancelotti's men have been given an easier draw against Bundesliga club Schalke, predicting Cristiano Ronaldo and Gareth Bale will cause havoc in the last-16 tie.
"Meanwhile, Real Madrid's tie seems somewhat more favourable to [los] Blancos," he added. "Schalke are able to play great football but Real Madrid start as favourites.
"Ancelotti has balanced the team and they have become much stronger in the past two months. When you lose the ball and you have Bale and Cristiano Ronaldo against you, you have to hope you have many players defending as they don't need many to do you harm."
Wenger reserved particular praise for Diego Costa when lauding Diego Simeone's men and thinks that Clarence Seedorf's side will struggle to progress past the Rojiblancos.
"I see Atletico have been very strong and are extremely good at getting results this season," the Emirates Stadium boss continued. "In La Liga they have kept track with Barcelona and Real Madrid and look particularly strong in defence.
"Moreover, they have Diego Costa who is extremely dangerous in counterattacks. I think Milan will have a hard time against Atletico."