The international break means players will return late to training, including in-form striker Salomon Rondon, who scored two goals for Venezuela against Panama.
Benitez said: "This period is quite difficult. Atsu is back now and was training on Tuesday and then on Wednesday we have a couple more problems but DeAndre and Rondon will come late. It will be difficult for us because sometimes they come to us and they say 'I'm fine'. But they can be tired. Rondon played in Miami.
"It's important for us to keep the communication with their medical staff and make the right decision about who plays. Some players are training now and feeling confident. The others, who knows?
"In the end it's a difficult decision. I remember when I was at Valencia and four players were called for international duty and they came back. We had a difficult game and I was asking them before the game: "'Are you fine?' They said yes but if I could make four substitutions after two minutes I would!
"We lost the game, they did not have the energy to make an impact and they were key players for us."