Liverpool boss Jurgen Klopp believes a proposal to introduce blue cards and sin bins to soccer does not "sound like a fantastic idea" initially.
It's understood that, in new trials to try and improve players' and officials' behaviour, blue cards will be shown to those dismissed for a 10-minute period.
It is understood that the initial trial phase will not feature top-level competitions to avoid players being in events with different rules concurrently.
Plans to publish details of these trials have been delayed until next month, but Klopp believes a blue card could present "more opportunities to fail".
He told a press conference: "I think we should keep it as simple as somehow possible, for the referees as well.
"It's a difficult job, often quite emotional when we speak about it more so because it's after the game, and I think the introduction of a blue card would just give more opportunities to fail as well.
"Because the discussion will be, 'it was a blue card, should it have been a yellow card?'.
"Now it's 10 minutes off - in the good old times it would have been a red card or only a yellow'.
"These kind of things just make it more complicated. If they want to test it I have no problem with testing if that's the first step to agreeing or it already being sure it will happen - I don't know that.
"It doesn't sound like a fantastic idea in the first moment but actually I can't remember the last fantastic idea which came from these guys, if they ever had one. I am 56 and - pah, never!"
Tottenham manager Ange Postecoglou also remained unconvinced by the proposals, adding his "biggest issue" in football is VAR.
"I don't think people will be surprised by my thoughts on it. I struggle to understand this urgency all of a sudden to bring in new things," he said.
"I don't know if there's that much wrong with the game as I see it. My biggest issue with the game right now is that VAR has changed the experience, whether you're a player, a manager or a supporter or whatever you are I think it's changed the experience of football.
"I assume that's a means to an end, that the introduction of technology is going to get us to a better place. I remain to be convinced about that.
"Beyond that, I don't know why a different colour card is going to make any difference. I struggle with this whole taking from other sports."
Australian Associated Press