HomeSteak
It came from Arteta and someone posted a clip of the fall on twitter, but tbf it doesn't sound like they actually know.
Speaking at his pre-match press conference ahead of Saturday’s clash with Leeds, Arteta said: “He [Saliba] is progressing. Unfortunately, he feels some discomfort in his back and we are trying to manage him in the best possible way. He’s not going to be fit for this game [against Leeds] but we are trying, he is trying to do everything he can to feel better and get back training, but not yet. We don’t know if it happened the previous game as he had a very awkward landing against Fulham but before that he was fine."