The 17-year-old signed his first professional contract at the Stadium of Light over the summer and has become a mainstay in the Black Cats' side so far during the 2024-25 term.
Rigg has featured in seven Championship matches for Sunderland, starting six of those, with Regis Le Bris's troops enjoying a productive opening to the season.
The England youth international managed his maiden goal of the term on September 21, when his audacious backheel finish won the match for the Black Cats versus North-East rivals Middlesbrough.
Winning five of their opening seven second-tier matches, Rigg and Sunderland occupy second spot in the Championship table, one point behind league leaders West Bromwich Albion.
Man United, Liverpool face Birmingham competition for Rigg
According to The Sun, a fresh horse has entered the imminent race for the services of Sunderland and England wonderkid Rigg in the calendar year of 2025.
The report claims that Birmingham are the latest side to express an interest in the 17-year-old ahead of the upcoming January transfer window.
It is understood that the League One outfit are preparing a £10m bid for Rigg in the New Year, as they look to lure him down to the third tier of English football.
Blues are no strangers to spending large amounts of money on promising talent, with Jay Stansfield moving from Premier League Fulham to St Andrew's @ Knighthead Park for an initial £15m over the summer.
As well as Birmingham, it is believed that top-flight powerhouses Liverpool and Manchester United are both interested in making a move for Rigg in January.
Could Rigg be the answer for Liverpool?
During the summer transfer window, Liverpool made the acquisition of a defensive midfielder their top priority, although their quest for recruits did not go to plan.
After agreeing a transfer fee with Real Sociedad, Euro 2024 winner Martin Zubimendi rejected a move to the Reds in favour of staying in Spain.
Since then, Arne Slot has used Ryan Gravenberch and Alexis Mac Allister in deeper roles in midfield, although Rigg would provide a more natural option in that specific position for the future.