Lionel Messi and Cristiano Ronaldo are "not as outstanding" as they once were, according to former Bayern Munich boss Ottmar Hitzfeld.
Messi has scored 43 goals in all competitions this term, more than any other player in Europe's top-five leagues, to help spearhead Barcelona's latest treble charge.
Ronaldo has managed a more relatively modest 24 goals in his first season with Juventus, but his hat-trick against Atletico Madrid sealed a Champions League quarter-final spot for the Serie A leaders and kept alive his chances of winning the trophy for the sixth time in his career.
However, both players were overlooked for the 2018 Ballon d'Or, with Luka Modric ending a 10-year Messi-Ronaldo duopoly by winning France Football's coveted prize.
And Hitzfeld believes each star is showing signs of decline, meaning a Premier League team is the most likely to become champions of Europe in 2018-19.
"I believe that English clubs have good chances again this year," Hitzfeld, who won the trophy as Borussia Dortmund and Bayern head coach, 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."
Messi's Barcelona face Manchester United in the quarter-final first leg at Old Trafford on Wednesday, the day Juve take on Ajax in Amsterdam.
On Tuesday, Liverpool play Porto and Tottenham meet Manchester City in the other last-eight ties.
Ronaldo, who last played for Juve on March 12, is battling to be fit following a muscle injury sustained for Portugal last month.