Town boss Jim Magilton was reportedly close to adding a defender to his squad as the transfer window closed on Monday. It seems likely the player was a centre-half, despite the Blues already signing Gareth McAuley, Pim Balkestein and Iván Campo during the summer.
Magilton is likely to make further attempts to land another new member of his backline when the emergency loan window opens next Monday, when he is also expected to add a left midfielder to the squad.
West Ham's Kyel Reid, Middlesbrough's Adam Johnson and Chelsea's Scott Sinclair are left-sided players who are known to be rated by Magilton, but the identities of potential defensive targets are less clear.
A report last week claimed the Blues had made an offer for Cardiff's Roger Johnson, although it eventually appeared that the club after the former Wycombe man was actually Hull City. Johnson, who Town asked about in June, recently signed a three-year deal at Ninian Park and now looks an unrealistic target.
When the emergency loan window opens next Monday, the Blues will able to take players from Football League and Premier League clubs for up to a maximum of 93 days. Town are likely to wait until close to the Reading game to complete their moves to make sure the 93-day period takes in the maximum number of matches.