Southgate may not rationalise it like this, but he must realise that the reason he HAD to pick White over Ward-Prowse is because he had already picked at least two liabilities in central defence (Maguire [may not be fit] and Mings [hopeless]). I've seen comments that the reason W-P didn't get the nod was because Henderson proved his fitness. I very much doubt that was the motivating factor (esp as Henderson was lumbering around not doing much in the 2nd half of the Romania game). The fact that it took the late injury to a RIGHT BACK to allow Southgate to bring in an extra central defender just underlines how feeble the selection process was.