From Rivals.com:

With as many as three freshmen set to start, a lot of critics like to
talk about the Trojans’ youth. But it would be more accurate to say
they’re inexperienced. Johnson is 19. Mayo will turn 20 before the
season starts. Jefferson turns 21 next month. Gibson is a 22-year-old
sophomore. This team is much older than it appears. It is also oozing
with talent. Mayo is a one-and-done player. Jefferson and Gibson will
leave for the NBA before their eligibility is exhausted. The backcourt
lacks depth, but the Trojans will make a legit run at the Final Four if
Mayo stays healthy.

Nice breakdown by Andrew.  Worth reading the entire thing.