Messi has scored 43 goals in all competitions this term, more than any other player in Europe's top five leagues as Barca maintained their LaLiga dominance.
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Ronaldo, 34, has managed 24 goals in his first season with Juventus, but his hat-trick against Atletico Madrid sealed a Champions League last-eight berth to leave him on course for a sixth title in his career.
And Hitzfeld, who won the trophy with Bayern and Borussia Dortmund believes both iconic figures, who were overlooked for the 2018 Ballon d'Or are not at their dominant level of the past leaving the English sides as favourites.
"I believe that English clubs have good chances again this year," Hitzfeld told Omnisport.
"They just have a lot of potential. And, maybe, because Messi is not as outstanding as in his best times, also Cristiano Ronaldo. He still makes his goals, but it will be difficult for Juventus to get into the last four, although they are always tactically excellently set up.
"I'm more likely to think of an English team, so Manchester City or Liverpool. One of them will certainly reach the final."