Captain Joe Root will keep a close eye on the fitness of Mark Wood and Jofra Archer in England's final practice session before the third Test against South Africa.
England need a replacement for James Anderson and would like to have one of their express pace bowlers charging in at Port Elizabeth on Thursday.
But Wood has not played a competitive match in the six months since the World Cup final and Archer is still battling the soreness in his right elbow which forced him out of the previous match.
Both men have been building up their workloads in recent days but need to make one last push to persuade Root.
Speaking before training on Wednesday, he said: "That decision hasn't been made. It's important to use today's session and make sure we've got a really clear understanding of where everybody is at.
"We need to find that out and make sure we're really clear going into a five-day game that they are able to stand up to the challenges that will bring, physically and mentally, having not played for a little while.
"It is the sensible thing to do to hold off, get more information on the pitch and more information on where they're at."
Wood tore his side in the World Cup final and has a long series of injury problems that have held back his career.
On the other hand he bowled a fearsome spell in the nets on Monday – visibly quicker than Archer, who appeared less able to unleash at full pace.
If that pattern continues in their final head-to-head he could find himself getting the nod at St George's Park, with Root seemingly keen to reward hard work in the nets.
"If they've proven themselves to be fit, if they've jumped through every hoop and worked very hard to get back there, you have to give them that opportunity," he said.
"With Mark, if you look at the last summer of cricket he played, he actually got through a lot of cricket injury-free which is testament to how hard he's worked on his rehab and making sure his body can cope with different things. He's been managed well by the medical staff.
"The reason we've been quite cautious in terms of rushing him back is that history. If he's 100 per cent, bowling at 90mph-plus, the skills he has at that pace are going to cause problems and will be a great asset in Test cricket."
