Tony Ralston is the man in possession at the moment but with Lee O’Connor failing to make the Champions League squad registered with UEFA it is an obvious area to strengthen.
Celtic have also asked the question about Nathan Byrne at Derby. He has also been flagged up by Parkhead scouting staff but Postecoglou has still to give the go-ahead on that move.
Derby have had a variety of financial problems in recent seasons with Wayne Rooney’s side escaping relegation to League One on the final day of the season.
After two seasons in the EPL Baldock would arrive with hefty financial demands while Byrne’s salary should be well within reach.
Another attraction is that the 29-year-old should be able to go straight into the Celtic squad while recent signings Kyogo Furuhashi and Carl Starfelt have to quarantine in London before starting their Celtic careers.
CLICK HERE for Byrne’s Transfermarkt profile.