The defenders left London for Switzerland on Wednesday morning after recovering from recent injuries.
Cole has shaken off a hamstring strain suffered in the FA Cup quarter-final replay win against Manchester United on 1 April, while Cahill has been passed fit following a minor knee operation on 30 March.
"Both are here and will train. They are fine," said Benitez.
"Obviously fatigue when you play so many games and travel around Europe is a key factor to consider.
"I praise my staff because we try to manage the squad in the best way possible. Still the team is [playing] good games and we have fresh legs in some players. We have to rotate, change and manage players."
Oscar came off at during Sunday's 2-2 draw at Liverpool with a groin problem but is also among the 19-strong party.