Poyet says O'Shea could play for any top six team.
"If you know John well and know what he is capable of, you realise why he played for United for so many years," said Poyet. "We are lucky to have him because he could be playing regularly in a top six team.
"A lot of players leave Man United and disappear, but not John. He is still an international and a big player for us and his country. That is why he is captain. It was an easy decision to make him our leader."