Defender Dan Ballard has signed a new four-year contract with Sunderland.
The 23-year-old is expected to start the season after missing the end of the last campaign through injury.
Northern Ireland international Ballard only joined the Black Cats on a three-year deal last summer.
Sunderland sporting director Kristjaan Speakman said: "Dan has proved that he's a standout performer at this level and he's growing in stature every day, on and off the pitch.
"He has a bright future ahead of him and he's extremely ambitious, and his decision to renew terms with us demonstrates that he feels his ambition is matched by that of the club.