That depends on how he performs in practice. If he shows he can follow direction, he'll likely be rewarded. If not...
Obviously dependent on performance in practice, but if he is doing well or seems to be trying, then carrots and sticks, man... even if its a sub for 30 secs - 1 minute. He's 19 - my primary focus at 19 was how to build a more effective gravity bong. Not saying give him time for nothing, but if he shows the slightest improvement in practice, I would make sure that is recognized in some way. A 1 minute cameo might work, or maybe just a positive statement at a press conference from Struber would have the same affect.
Subbing out a sub and then saying he wasn't good enough doesn't seem like the way to build up a 19 year old, even if he is a professional athlete. I trust Struber knows what he is doing, but if I was Struber, I would be looking for any slight improvement so that a carrot can be given.