Ledley was a major plus point in what was his tournament debut against France on Sunday.
He was outstanding in central defence against the likes of Henry and Trezeguet before France's late, late show turned a 1-0 England lead into 2-1 French win in injury time.
Switzerland are next in another crucial game on Thursday - if England lose, they are out - and first-choice centre-half Terry is fit again and looks set to return in place of Ledley.
It has left Eriksson with a dilemma and he said: "It would be difficult to leave Ledley out after a performance like that but on the other hand there is no reason to keep John Terry out if he is fit.
"It's a good problem to have. But Ledley will not be that disappointed. He will understand."
Meanwhile, Eriksson reiterated his praise for Ledley after Sunday's faultless display.
"I have always been impressed by what he did in practice," he added. "He's very intelligent because you tell him about something and he does it.
"It was the same against France. I don't remember him making any mistakes at all. It was a good choice to play him."
England boss Sven-Goran Eriksson has admitted it will be difficult to leave out Ledley King against Switzerland - but at the same time insisted he has no reason not to play a fit John Terry.