I don't know anyone who strives to be average. "Strive average" would almost be an oxymoron. But how many people truly understand both the meaning and the requirements of 'exceptional'? Where do you have to set the bar even to dream about becoming exceptional?
'Exceptional' isn't monolithic. Wealth might connote exceptional performance...or not. Wealth might be inherited, obtained corruptly, or won. Jesse Livermore achieved and lost exceptional wealth via speculation multiple times and ultimately committed suicide. Mother Teresa clearly was exceptional but not wealthy. Within the context of sport, you might achieve notoriety for a certain skill (e.g. rebounding) but not achieve overall exceptional performance...although that in itself would be an outlier.
The underpinnings of 'exceptional' reflect preparation and performance. Bill Walsh had his "Standards of Performance" and John Wooden had notes from every practice. When we think about our exceptional colleagues, we probably think first about process and performance but at their core we value their character, commitment, and integrity. Brad Stevens says "the game honors toughness" but I think we honor character first.
What do we tell a player who asks "what will it take to become exceptional?" I first answer the question with a question? "What price are you willing to pay?"
Bill Bradley developed a core program of practice for years starting as an adolescent of three hours a day after school and eight hours on a weekend day. He knew that he wasn't the most athletic player, therefore developed superior skills through force of time and will. He partnered this with academic skills to excel at Princeton, earn a Rhodes Scholarship, and become a US Senator...as well as achieving first team All-America status twice, winning the Final Four Most Outstanding Player award, and two NBA championships. He paid the price and reaped the full measure of reward.
Paying the price means sacrificing other activities that your peers do not. In addition to time, exceptional basketball will mean individual athletic training and skill development, eating better than your peers, getting more rest, fewer social activities, and zero contemplation of alcohol or drug excess. Some will consider you 'different'. You have to accept and embrace that uniqueness.
Easily throwing around terms like greatness and exceptional disservices the few who actually achieve them. And there's no guarantee that you achieve greatness, only peace of mind knowing that you have done your best.