They don't need to be a world class striker, though, to come on and affect matches. Giroud for instance would have been perfect. Maybe even someone like Chicharito or Defoe. Just one of those players with that knack of nicking a goal when it matters against a team that's shut up shop.
Edit: my issue is that we have some fantastic attacking players, but Mane, Bobby, Salah, and on my understanding of him Fekir are all very similar, and Ings and Solanke are similar but not as good. We want a bloke who can stand in the box and score ugly goals when necessary.