Sunderland's defensive concern which could impact Swansea, Norwich, Leicester and Southampton fixtures

Sunderland centre-backs Luke O'Nien and Dan Ballard are both walking disciplinary tightropes ahead of Saturday's match against Birmingham.

Both players have picked up nine yellow cards this season, meaning they are just one booking away from receiving a two-match suspension. Sunderland full-back Trai Hume has also been shown eight yellow cards in the Championship this term.

EFL rules state players who are shown 10 bookings up to and including the 37th league game of the campaign will have to serve a two-match suspension. Sunderland have played 32 Championship matches ahead of this weekend's game against Birmingham, with their 37th coming away at Southampton on Saturday, March 9.

Sunderland will also face Swansea, Norwich and Leicester before the 37-match cut-off point, with the possibility that both Ballard and O'Nien could be suspended at the same time. That was the case earlier in the campaign when the pair were unavailable for November's 3-1 win over Birmingham after receiving five yellow cards each.

That win over the Blues is the only league game O'Nien and Ballard have missed this season, as Jenson Seelt and Nectarios Triantis started at centre-back for Sunderland. Triantis has since joined SPL side Hibernian on loan until the end of the season.

Sunderland have also been without defender Aji Alese in recent weeks due to another injury setback, but have brought in Leo Hjelde from Leeds. The Norwegian has played at left-back since joining the Black Cats but has said his preferred position is centre-back. Timothee Pembele's return from injury will also provide another option at full-back, with Dennis Cirkin and Niall Huggins out injured.