Brazil legend Ronaldo, who represented both La Liga giants, believes they are the teams to beat but insists the English clubs could cause an upset.

“The favourites to win UEFA Champions League are always the same: Real Madrid and Barcelona are ahead of the rest,” Ronaldo, the global ambassador for competition sponsors Santander, told Goal .

“Real Madrid, because of their history and tradition, and that they have won four of the last five titles, including three in a row. They are always among the favourites for this competition.”

“Many of the teams have reinforced [in the transfer window], but it’s a very difficult competition when the group stage ends and we get to the knockout rounds,” he said.

“The Spanish clubs know this very well, but I think we might be surprised by the English sides, because they are very strong and have the economic power to buy top players.”