O'Connell is higly-regarded within the corridors of power at Ewood Park and is tipped to be pushing for the first-team next season.
The 19-year-old enjoyed successful loan spells at Rotherham and York City last season, making 23 appearances during his time at both clubs.
O'Connell, who has represented England at Under-18 level, caught the eye of several Premier League clubs when captaining England Under-19s during their recent European U19 Elite Round qualifiers.
The powerful left-sided central defender picked up two man-of-the-match awards during the qualifiers and his suitors are now stepping up their interest.
The likes of Tottenham, Newcastle, Cardiff, Aston Villa and Swansea are all thought to be monitoring his situation at Ewood Park as they prepare to test Blackburn's resolve to hang onto the prize asset.