The 20-year-old forward has been linked with a move away from the Black Cats after finding his first-team chances limited on Wearside.
Scunthorpe United are the latest team to reportedly register an interest in Watmore, but Poyet is eager for him to develop at Sunderland.
"He's the player who you want at the football club. He's got plenty to learn, but he's desperate to do it," the Uruguayan told the Sunderland Echo.
"We had, I don't know how many clubs call us, but we believe he needs to be here and I think he agrees as well. It's important that he plays football at a better level, but, at the same time, he needs to learn what we want."
Sunderland are back in Premier League action on Saturday when they travel to Southampton.