Jamaal Lascelles is out of Newcastle United's visit to the Amex Stadium.
The club's captain will miss tomorrow's game against Brighton and Hove Albion with a stomach bug.
Benitez was already without Miguel Almiron, Florian Lejeune and Sean Longstaff, who have all suffered season-ending injuries.
Almiron was forced off against Southampton last weekend with a hamstring injury.
“The bad news is we have Longstaff, Lejeune and now Almiron," said Benitez. "Three weeks (for Almiron), and we will see how we progress.
"Lascelles, we have lost, because he has a stomach bug. Illness, nothing serious.
"Miguel's fine, he went to see a specialist in Spain, started his treatment and everything going to plan. It's quite positive, and he's a good professional."
Isaac Hayden and Fabian Schar also suffered injuries in Newcastle's 3-1 win over Southampton, which secured the club's Premier League status.
However, Benitez expects them to be OK for the Brighton game.