Though Roberts entered Friday's game with the Minnesota Twins hitting only .237, he also entered as the Yankees leader in hard-hit rate this season.
What's hard-hit rate?
It's a stat kept by video-tracking services that provide data to major-league teams. They rate every batted ball as hard-hit, medium-hit, or soft-hit based on video review. Those tracking look for favorable velocity off the bat and for contact on the sweet spot of the bat. Hard-hit rate is simply hard-hit balls divided by total at-bats (plus sacrifice flies). The average non-pitcher's hard-hit rate is usually between 16 and 17 percent by season's end. Jacoby Ellsbury and Mark Teixeira entered Friday ranked second on the Yankees at 18 percent. Victor Martinez leads the majors with a 27 percent rate.
Roberts, who entered the day with a hard-hit rate of 19 percent, hit five balls on the button in Friday's win, netting three doubles and a triple, along with a line-drive out. He's the first Yankees player with three doubles and a triple in the same game since Red Rolfe did so against the Tigers on Aug. 11, 1936 (a game in which Lou Gehrig homered) and the first Yankees player with four extra-base hits in a game since Alex Rodriguez on April 18, 2005.
Though Roberts is hitting the ball hard, he hasn't had as many days in which he reaped the rewards as you might expect.
The average player gets a hit on 70 percent of his hard-hit balls. Roberts entered Friday with only a 60 percent success rate (down from his 70 percent success rate last season). If Roberts had matched his hard-hit batting average from 2013, he would have entered Friday hitting 20 points higher than he was (.257 instead of .237). He got a chunk of that 20-point differential back on Friday, raising his season batting average to its current .248.
"We've said all along that his numbers were not really indicative of how he's swinging the bat," said Yankees manager Joe Girardi after the game. "We think he's hitting the ball pretty hard. He just didn't hit them at people [today]."