Benitez believes the squad needs reinforcements after his initial assessment of the squad.
"If you're not winning and you analyse the players who have played almost every game, there aren't many players here," said Benítez.
"There were 19 in the league, and now it's 20 with Marko Marin [who appeared as a substitute against Fulham]. They'd been playing fewer players than other clubs. I'm not here to criticise, but that's the reality.
"They'd played so many games, two or three a week and massive games in the Champions League, that the players were getting tired. You can't give them a rest either, because there's no time. I explained what I'd seen, my ideas on things and my explanations."