Jalen Reagor 40's speed was 4.47, which is good (74th-percentile), but not elite especially for a 5'11" player.

However, his burst score -- which means stop-and-start acceleration -- is 140.4 (99th percentile). That is in fact, elite.

Another good indicator is Reagor broke out as a freshman at age 18, with eight touchdowns and 576 yards. Then went for 72 / 1,061 / 9 + 170 yards and 2 more TDs rushing as a sophomore at age 19. Very encouraging stuff.