The Scotland international was ruled out of the last three months of the season with an ankle problem as he missed his side's miraculous escape from relegation.
Poyet has admitted that the 27-year-old is eagerly anticipating the start of the new campaign after his injury struggles.
He told the club's official website: "Fletch came back a week early to make sure he started running with no reactions. I saw him yesterday and everything looks fine.
"He's excited. People don't know sometimes that the players are like any of us. When you like so much to play football you're excited about the chance to go back."
Fletcher scored three goals for the Black Cats last season.