That's my concern as well. We would have the possibility, if he stayed fit, of playing Sturridge as the number 9 and dropping Firmino back in to midfield against those type of teams. Sturridge still has the instincts and movement to make space in the box, even if he doesn't have the outright pace anymore, and Firmino has the vision to pick out passes and play the fancy flicks that could make space for the players around him.
Would certainly prefer Coutinho to stay for another season, assuming he gives it 100%, but I think we have options.