If someone else had said this I'd take it with a very large pinch of salt, but the fact Klopp said it certainly raises questions. I mean, he knew we were signing him over two years ago - has he not been putting in the work? Was it not communicated to him it would be an issue? Is it likely to be resolved any time soon?
I'm not sure its the case with Keita, but I don't think language barriers should ever be an issue for a modern professional player. Given the money in the game, players could have 1:1 tuition at the club or at home, especially as communication is such a key part of the game and Klopp's philosophy.
I'm also sure I read somewhere that the club demands that players speak to each other in English at all times, as that's the language to communicate on the pitch. I'm sure the Brazilians and Dutch have their own conversations socially in their own language, but surely during training, meetings, and any time spent at the club it should always be consistent.
I always found it odd when managers who can't speak English join the Premier League, and a year later can barely even give an interview (Pochettino springs to mind) - how on earth are they communicating with their own players and staff?!