One of the biggest differences is the shot clock. The NBA shot clock is 24 seconds, while the NCAA shot clock is 35 seconds. Another key difference is that NCAA plays two twenty minute halves, while the NBA plays four twelve minute quarters. Both leagues have very strict rules and hold their players to a high standard. They both have nearly the same substance abuse policies. Another minor difference is the number of timeouts each league ives teams, NCAA teams get four, 75 second timeouts, and three, 30 second timeouts. However, NBA teams get six, one minute timeouts, and two, 20 second