Brown was forced off with a twisted ankle early on in Thursday’s 4-2 loss to Slovenia, with his replacement Cathcart then withdrawn in the 76th minute with a groin problem.

With Dan Ballard having missed that fixture with an ankle problem, O’Neill’s defensive resources could be stretched to the limit in Astana.

While O’Neill has Eoin Toal and Brodie Spencer in the squad, Paddy McNair is a regular in defence for Middlesbrough and Southampton midfielder Shea Charles dropped into the back four at times in Ljubljana.

Northern Ireland’s qualifying campaign has been wrecked by an injury list stretching deep into double figures and Thursday’s defeat effectively ended any hopes of making it to next summer’s finals in Germany.