Doak and Hefferman added to injury-hit Ireland squad in South Africa

An Irish Rugby Football Union statement said "Connacht hooker Dave Heffernan and Ulster scrum-half Nathan Doak have been called up and the duo have linked up with the squad in Durban".

The players flew to the Indian Ocean city, venue for the international on Saturday, after scrum-half Craig Casey and hooker Dan Sheehan were ruled out by injuries sustained in the first Test.

Sheehan could be sidelined for up to nine months by a left knee injury during the 27-20 loss to the world champion Springboks in Pretoria last Saturday.

Casey is recovering from concussion after being tackled by South Africa lock RG Snyman, who will play for Leinster next season after being a teammate of Casey at Munster.

Heffernan has been capped seven times by Ireland and joins likely starter Ronan Kelleher and Rob Herring as the hooker options for head coach Andy Farrell.

Veteran Conor Murray is expected to replace Casey in a starting line-up to be announced on Thursday with Caolin Blade and uncapped Doak the other scrum-halves in the touring party.

Prop Andrew Porter is set to start despite suffering a cut to his hand in the first Test between South Africa and Ireland, who are first and second respectively in the world rankings.

Adding to the concerns of Farrell, centres Robbie Henshaw (head) and Bundee Aki (shoulder), winger James Lowe (thigh) and full-back Jamie Osborne (groin) face fitness tests.

A win for Ireland on Saturday would tie the two-Test series against the record four-time World Cup champions.

The countries have met 29 times from 1906 with South Africa winning 19 Tests and Ireland nine with one drawn.