Desmond was already at the end of his rope; at this point, the damage his body had sustained was beyond the point where he could support himself in combat. If it wasn't for the cocktail of potions Desmond had ingested, he wouldn't be able to stand up anymore.
However, even that came at a cost; Desmond's wounds weren't healing and were only stable at best. Meanwhile, Desmond was essentially burning off the medicinal efficacy of the potions as fuel to keep fighting.
Desmond was fighting on borrowed time, and he knew it, so his number one priority was getting out of this place safely with Cecilia. To do this, Desmond had to get past the three knights in front of him, but more importantly, he had to get past Camila.
