Mental toughness is a phrase bandied about rather liberally. I have had many athletes come to me with a reputation of poor mental concentration.
In almost every case I found it was not a mental problem, but a practice problem. If you are not logging your hours on the court, you will not be performing at the level you are capable of. If you are receiving poor coaching and practice poor footwork, you will also suffer. At crunch time, the automatic response the athlete needs demands rehearsal. Therefore it is not a mental thing, it is a practice thing.
Take a lesson from police or military training. Those folks practice maneuvers over and over so when the training is needed for real, there is no thinking about it. Response is automatic.
I recently saw a lower ranked pro post that nobody should ever criticize a professional player because all of the pros work hard on their game. Really? I do know that the pros work in varying degrees on their games but not everyone works real hard. Besides, it is never about how hard you train, but how smart you train.
If you are not winning, you are not executing. If you are not executing you are not practicing correctly or enough!
So is it a mental toughness problem or a practice problem?
Rehearse to go from worst to first!