Sometimes the best way to determine if a manager is going to succeed is to throw them into the ring and see if they can jump their way out of the fire. It isn't the preferred method but it does work when the training and support have already been offered. People perform their best or worst under direct stress in their environment.
We can send managers to training, provide education and mentor them. At the end of the day we will need to test their skill in some way. This usually happens when we need them to show they can perform.
The real environment is very different than the academic or training environment. It is based on actual challenges that don't have hard and fast rules. Theory becomes reality and practicality takes precedence.
While some managers may fail some will also succeed. They will be able to handle the rigors and make their way through the challenge to the other end. They can use their abilities to keep calm, motivate and act to achieve their objectives.