The defensive conundrum Tony Mowbray has been weighing up at Sunderland in recent weeks

After watching his Sunderland side comfortably beat Watford at the Stadium of Light earlier this month, Tony Mowbray was thinking aloud in his post-match press conference.

Mowbray was full of praise for his defensive unit, with Niall Huggins on this occasion the headline act after his brilliant individual goal in the first half.

Huggins' form had gone some way to allaying any concerns about the depth in the full back positions, but in central defence the question remains.

Which, as Mowbray explained, isn't really the fault of either Jenson Seelt or Nectarios Triantis - it's just that the two players in front of them have been so good, rotation is out of the question.

Yet injury or suspension is at some stage inevitable, and Mowbray's point was underlined within days when Huggins picked up a (hopefully minor) injury against Middlesbrough. Seelt came on at right back in what was by some distance his longest and toughest assignment since joining the club.

Mowbray knows he will be in the same position again at some stage in the near future. Dan Ballard has picked up a thigh niggle on international duty and while he is expected to be fit this weekend, it highlights the importance of squad depth. Ballard is also on four yellow cards for the campaign, and so at some point is likely to serve a suspension.

It means Mowbray's challenge in keeping Seelt and Triantis ready for when they will undoubtedly be called upon is more pressing than ever.

"You look at our defensive unit, Jenson and Triantis need to keep playing U21s football so that they can show me [that they're ready]," Mowbray said.

"Somewhere down the line, our two centre halves have been immense but at some time... they won't play 46 games a season, and so the other lads have to be ready.

"We have to keep giving them game time. It's a very difficult balance between them being on the bench and not getting those minutes, then the next game comes around [quickly]. When do get those games you need in? It's difficult because it can then impact the first team games, but those minutes are really important.

"I've said to them both, I know they signed to the club to play and progress their careers, but the two lads at the moment are real beacons to hold up to young professionals, really, with how they do that job."

Mowbray's options at centre back will also be bolstered by the imminent return of Aji Alese. Alese has not yet featured this season but returned to full training before the international break and so could feature in the U21 side next week.

While the former West Ham United defender has played the vast majority of his football since joining Sunderland at left back, he is comfortable playing in central defence.

Dennis Cirkin is also nearing a return to fitness from a hamstring problem, though Mowbray has previously said that he does next expect him to be back immediately following the international break.