The power of Mookie Betts' disciplined aggression

This story appears in the September 10 issue of ESPN The Magazine. Subscribe today!

Last November Mookie Betts rolled a 300 game in the PBA World Series of Bowling. This spring he solved a Rubik's Cube, on television, in under two minutes. Primarily a second baseman in the minors, Betts converted to the outfield upon reaching the Boston Red Sox four years ago and has now saved more runs for his team since 2016 (76, through Aug. 19) than any other major league fielder.

These facts are cool. More important, they testify to Betts' most admirable trait: his willingness to work hard at endlessly repetitive tasks, picking up patterns and fine-tuning again and again to improve the expression of his…