Liverpool manager Jurgen Klopp has criticised the Premier League for a "lack of leadership" over the return to three substitutions in the competition this season.
Clubs could use five substitutes last season when the league restarted in June after a three-month hiatus due to the coronavirus pandemic, but they voted against it for the 2020-21 campaign.
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Clubs participating in the Champions League and Europa League can still use five substitutes and Klopp said English clubs are at a disadvantage due to the rule change.
"All other leagues, pretty much, in the world have five subs and England has three subs," he told a news conference ahead of their Premier League match against West Ham United.
"That makes it a massive challenge. As you know seven clubs in the Premier League play three times a week and then we travel and that makes it tricky but we all have to deal with it. We will see how it will end but it's the most challenging season for sure."
When asked whether the rule should be reverted back again, Klopp replied: "Yes, but I don't think it's possible because of this system.
"For me, it's a lack of leadership to put the question on the table and say what do you want with that. It should have been differently sold, if that's the right word, with more information, knowing more what can happen and all these kind of things by Richard Masters [Premier League chief executive].
"We never asked for any advantage, one of the top seven clubs. It's because we knew our schedule, it will be incredibly difficult to have the best games every weekend in the Premier League as well. I think we should overthink it again to be honest."
Manchester United boss Ole Gunnar Solskjaer also questioned the decision against five substitutions while Manchester City's Pep Guardiola called on the Premier League to reintroduce the rule.
Liverpool will be without Virgil van Dijk and Fabinho for the foreseeable future due to injuries and Klopp said the league needs to do more protect footballers.
"My concern is the welfare of the players," he added. "Every now and then, it's a really big thing to talk about the mental welfare of the players but we have to talk about the physical welfare of players much more often because the boys always want [to play]. Even if they can't, they still want [to play] but we have to make fixture lists and schedules where they can.
"But this is a difficult year. It was always clear that we put in a season with nearly the same amount of games in a short period of time and we all wanted it, I wanted it, everybody wanted it.
"But that's the same in other leagues with lesser teams and they find it challenging. Ask in Germany, they have two teams less, different cup competitions and not that many games and for them it's really challenging.
"We have more games and we can only change three times and I remember the discussions from pundits saying with five subs it's not the same game anymore. No, it is not the same game anymore because time is different and we should have thought this 100% through.
"Don't see it that anybody wants an advantage, just see it for what it is. It's about players' welfare and nothing else and it was always [like this]."