When did he fall in price? Saturday night/Sunday morning makes a little more sense I suppose if people transferred him out ahead of the deadline on Saturday. People scared of him going to Anfield.
If it was after that then it seems shortsighted. Even if it was Saturday night, people could always have decided to bench him for Anfield, knowing that Southampton was after that.
Would think he'd be a rotation option at his price point anyway, and that benching him for certain games would come with the territory.