Strengthening his back four has been a priority for Bruce all summer following John Mensah's return to Lyon after a loan spell on Wearside with no prospect of a permanent deal.
While he hopes to make a breakthrough within the next week or so with Argentinian full-back Marcos Angeleri, who is awaiting an Italian passport before he can sign, finding new recruits for the heart of his rearguard is proving more problematic.
Top target Heiko Westermann was on Tuesday poised to join Hamburg from Schalke, while the Black Cats' interest in Manchester City's Nedum Onouha has cooled.
Bruce is awaiting an answer from former Arsenal man Sol Campbell, who is currently away on honeymoon following his marriage at the weekend.
But the 35-year-old has spoken to several clubs, including derby rivals Newcastle, and is expected to make a decision when he returns, although the financial aspects of any deal for a man who will celebrate his 36th birthday in September could prove key.
However, Sunderland have other irons in the fire and Press Association Sport understands Bruce could be ready to turn to Titus Bramble, with whom he worked at former club Wigan.
The 28-year-old has rebuilt his career at the DW Stadium after an error-strewn five-year spell at Newcastle and is highly-rated by the former Manchester United defender.
Bruce has previously played down speculation linking him with a move for Bramble and any interest is at the formative stage.