I don't even think he was that bad against Liverpool.
94% pass success. Admittedly a lot of those were back to Holding, but there were a few moments where he did well to keep the ball under pressure and passed it to someone else in space. Put it this way, there were many others, including a few favorites and his midfield partner Xhaka, who performed far worse. He's average and him and Xhaka make up a dire pairing, but he's a decent player to come in for EL and Cup games and as deep cover.
If all you're going to get for him is a couple of mil you're better off keeping him.