That beating will certainly leave a bruise on Enzo Maresca and his side.
They were outplayed from the first minute today, and in truth, they could have easily conceded two, or three, more.
It may only be pre-season, but Maresca has a lot to think about. Shipping four against Celtic isn't the best really, is it?
They still have three more friendlies in their tour of the US, two of them are against Man City and Real Madrid, though...
They will need to play a hell of a lot better than that to get anything from those matches.