True! It's not an easy job , thus IMO PSG lacks a better coach to be candid, even when they had a perfect squad they couldn't win it(maybe too much of star player but I still feel they need a better coach).
Which PSG coach are you referring to?
Mauricio Pochettino, Thomas Tuchel, Unai Emery, Laurent Blanc, and Carlo Ancelotti are few former coaches of PSG. None of them are bad coaches, even Ancelotti is the most successful coach in football history, especially in UCL. I think PSG is just unlucky that they always failed to win UCL.
https://www.worldfootball.net/teams/paris-saint-germain/9/Well, Luis Enrique is the coach of PSG now. He is also a great coach, but not sure if he is able to lead PSG winning UCL trophy. FYI, he also ever won UCL trophy with Barcelona.
https://www.transfermarkt.com/luis-enrique/erfolge/trainer/6499To win the UCL league you don't have to win the domestic league. This has been proven by several clubs as you mentioned. Indeed, winning the domestic league will be a factor in proving their consistency in every match.
Of course, winning or leading domestic league is surely not the requirement to win UCL trophy. Even if winning or leading the domestic league indicates the strength of a club, they can perform differently in UCL. On the other hand, even though a club doesn't perform very consistent in the domestic league, it is possible that they play consistently in UCL matches.
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