Lambert is confident Delph is able to perform on the international stage if and when the former under-21 star wins his first senior cap.
"If England did call him in and give him a chance he wouldn't let anybody down, but that's up to the England manager to assess," he said.
"I don't know if he's got a chance, but I always think there's one surprise.
"Whether it's Fabian or someone else, I don't know. But at the minute he's playing really well for us, which is my concern at the moment."