We've got Gent, Halliday and Nicholson that can operate on the left side of the team in various full back/wing back combos. O'Donnell can play there at a push too.
So while it would be a blow, it's not as bad as if we ended the window with one striker.
On a related note, I heard the other day that hamstring injuries in the EPL are up around 47% this season. There is a theory that VAR is responsible to some degree. Partly, because players are having to stop for a few minutes multiple times per game and stand around without warming up again, and partly because games are being extended to 100+ minutes putting extra strain on tired muscles and ligaments.