The 24-year-old midfielder joined Nottingham Forest last summer but failed to establish himself in Steve Cooper’s squad.
O’Brien managed only six starts in the league before being sent out on loan to DC United in the winter transfer window.
His performances for Wayne Rooney’s team garnered interest from Sheffield United.
However, Nottingham Forest refused to let O’Brien join their Premier League rivals despite the Blades’ strong interest in him.
Sheffield United are not the only suitors for the midfielder, as several Championship outfits are showing interest in him.
It has been claimed that O’Brien will leave the Tricky Trees this summer on loan to join a Championship outfit.
The midfielder has 123 Championship appearances under his belt and now all eyes will be on him to see where his next destination will be.
