Here's the single problem for Rizzo

Anthony Rizzo's batting average on medium- and soft-hit balls is just .142, about 80-85 points lower than the average player. David Banks/USA TODAY Sports

CHICAGO -- It took some extra batting practice and a move to the No. 2 spot in the batting order, but Chicago Cubs first baseman Anthony Rizzo broke out of his slump with two home runs Wednesday night in an 11-6 loss to the Washington Nationals.

Rizzo was previously 2-for-24 during the Cubs' homestand.

But the question lingers: Why has Rizzo been slumping in the first place? It's easy to say it's both mechanical and mental, because those two factors always intertwine.

Basically, he needs to hit more singles.

As Cubs manager Dale Sveum told me Tuesday, it's partially because Rizzo isn't punishing the four or so belt-high fastballs he sees a game. Any hitting slump is about fastballs, which is why Rizzo and Starlin Castro were practicing hitting them hours before the game.

Rizzo rates around average when hitting pitches of 93 mph and up with a .264 batting average, according to Mark Simon from ESPN's Stats & Information group.

With small samples of those plus fastballs, that number bounces around, but Rizzo's 93 mph-plus fastball batting average rates him just a tick above the average hitter and below the elite level.

He's still above average in slugging and OPS against the heaters, albeit with just four home runs, which is average to below average for a first baseman.

Rizzo's first home run Wednesday came on a 94 mph fastball from Ross Ohlendorf. His second was on an 80 mph changeup.

While it's correct to focus on OPS over batting average, especially for a hitter like Rizzo, the 24-year-old needs to be a more consistent hitter, and collecting more singles will help.

Compare his overall power numbers, collected in a streaky manner or not, to those of Andrew McCutchen, the steady MVP candidate for the first-place Pittsburgh Pirates.

Going into Thursday's games, Rizzo, a left-handed hitter, has three more home runs (20-17) and four fewer RBIs (68-72) than the right-handed McCutchen. They both have 32 doubles, and McCutchen has only one more triple (3-2) in a similar number of at-bats (469-464). They have similar walk percentages (11.2/10.6 percent), though Rizzo strikes out more (99-81).

But McCutchen is batting .319 compared to Rizzo's .232 because he has 41 more singles. McCutchen's BABIP (batting average balls in play, which doesn't count home runs) is .354, compared to Rizzo's .254.

"McCutchen is an unbelievable fastball hitter," Sveum said. "The bottom line is it's not about not hitting the breaking ball, it's laying off the not-a-strike breaking balls and never missing the fastballs."

With the help of the Inside Edge scouting service, ESPN Stats & Information tracks a statistic called "hard-hit average." Every at-bat is charted, and each batted ball is described as hard-hit, medium-hit or soft-hit. Several teams, including the Cubs, have their own methodology for measuring "hard-hit average." (Simon tweets out a weekly hard-hit leaderboard, as seen here.)

Rizzo is one of a few players with high "hard-hit averages" and low batting averages. After his two-homer game, his hard-hit average is .696, up a little from last year's .694 average during an impressive debut with the Cubs. The average player, though, is hitting around .720.

His batting average on medium- and soft-hit balls is just .142, about 80-85 points lower than the average player. On ground balls hit medium or soft, his average is .094, which, as Simon notes, "is as bad as it gets." About 70 percent of singles are considered medium or soft, according to ESPN.

According to ESPN stats, Rizzo has 38 soft or medium hits this year, while McCutchen has 63 in the same number of at-bats.

With a focus on collecting base hits, Rizzo can boost his batting average and at the same time, his team's fortunes. Of course if it were that easy, he wouldn't be struggling in the first place.