Losing Robbie Henshaw and Jared Payne in the space of four days would seriously harm our chances of winning the Castle Lager Series.
Henshaw is set for surgery on damaged knee cartilage while Payne has emerged as Ireland's biggest fitness concern ahead of the third and final Test against South Africa.
The series is tied at 1-1 and Ireland have not yet ruled the Ulster back out of Saturday's decider.
Payne left the field, last weekend, after 75 minutes. He was suffering badly from cramp and was barely able to walk in the immediate aftermath of the 32-26 loss.
Ireland did not train on Monday or Tuesday so today's session in Port Elizabeth will be Payne's best chance of proving to management that he can play. There will be a final chance to impress upon the management that he is ready to play on Thursday morning.
Payne played 50 minutes of Ireland's February defeat to France with a Grade 1 hamstring tear so he is made of stern stuff. He may attempt to tough this one out on Saturday.
Were Payne to miss out, Joe Schmidt would be left with a call on who will play outside centre and fullback. The Kiwi could have filled either role having played frequently in both roles, for province and country, in recent seasons.
Stuart Olding and Keith Earls are both fullback options but may be required at inside centre and on the left wing. Ian Madigan has also played at 15 but would, most likely, be needed as versatile backline cover off the bench.
That leaves Craig Gilroy or Tiernan O'Halloran. Gilroy had a decent game in the Second Test while O'Halloran made his debut off the bench when he replaced Payne around the 75 minute mark. He enjoyed a fine season with Connacht so would have the edge on the Ulsterman.
