Might just have been feeling a bit under the weather, coming from Turkey to Liverpool and it being fucking freezing n all that. I don't think it was anything more sinister than bedding him in.
Although I 100% don't agree with it as Niasse should never be starting a Premier League match, unless we're really desperate, as you can't build any kind of a platform with a guy who's running round like a headless chicken and not offering any structure to his play. He has a place and it's playing against tired defenders when we need a goal poacher or someone to make something happen, somehow.