28 Sep 2020 11:50 AM +00:00

Pittsburgh Pirates: Gregory Polanco and predicting performance


Everybody makes mistakes.

On April 4th, I wrote this piece about Pittsburgh Pirates outfielder Gregory Polanco and concluded that he would have a bounce-back season. This writer thought Gregory Polanco would contribute to the Pittsburgh Pirates' success if they kept up their hot start.

The Pirates have remained one of the better teams in baseball. Gregory Polanco has not remained one of the hottest players in baseball. Through May 15th, Polanco has a .226/.333/.474 slash line and a 116 wRC+, largely due to his hot start. After April 4th, however, he has had a .217/.304/.450 slash line and a 101 wRC+. He had a batting average below the Mendoza line through a significant portion of time after April 4th. His WAR even dipped below 0, making him less productive than a random minor leaguer, but still more productive than Ian Desmond. On the surface, I may have made a mistake. But despite Polanco’s below replacement level production since April 4th, he has shown signs he may still have at least a productive season.

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Still Showing Patience

Even during his struggles, Polanco has remained patient at the plate. His 13.9% BB% is well above the league average of 8.9%. Even though he walked in only 10.1% of his plate appearances since April 4th, that is still above the major league average this season. Polanco has also never recorded a walk rate higher than 10%, and he only got higher than 9.0% in his rookie season.

Small sample size might have caused this uptick in walks, but he has made a few notable adjustments. So far in 2018, he has recorded a 43.8% swing rate, the second lowest swing rate of his career, behind his rookie season. He has also swung at fewer pitches outside the zone, recording a 26.5% swing rate at pitches outside the zone, yet again the second-lowest rate of his career and lowest since his rookie season. But he has also recorded lowest contact rate (74.9%),  highest swinging strike rate (10.9%), and highest K% (22.1%) of his career in 2018, showing that when he swings, he is swinging harder. More on that later.  

The patience has paid off. Despite the repulsively low batting average, Polanco’s on-base percentage since April 4th is only a few points below the league average, and his season on-base percentage remains 14 points above the league average. Polanco retained some value offensively by getting on base through walks.  


Still Hitting Hard

When Polanco has swung and made contact, he is still hitting the ball hard, as his .450 SLG since April 4th shows. With 12.6 barrels per batted ball event, Polanco ranks 47th in the majors among players at with least 50 batted ball events. He is ahead of players such as Charlie Blackmon, Carlos Santana, Mike Moustakas, and Edwin Encarnacion. That is a list of players that a good version of Gregory Polanco should appear on. While the high barrel rate shows that he still makes quality contact frequently, Polanco has experienced a dip in his power.

Since April 4th, Polanco has experienced a noticeable decline in his average exit velocity. After averaging 92.4 miles per hour of exit velocity in the first four games of the season, Polanco averaged 89.4 miles per hour of exit velocity in the next 32 games. That average exit velocity almost exactly matches his 2016 average exit velocity, so while he has not hit the ball as hard as he did very early in the season, Polanco still gets a hold of a few baseballs. Since April 4th, he has a 31.9% hard contact rate, below the league average 34.8% hard contact rate, according to FanGraphs. But Baseball Savant, which uses Statcast’s exit velocity data, says Polanco has a 38.46% hard-hit rate since April 4th, a much better 125th in the majors among majors with at least 50 batted balls, putting him right at the median value (For now, focus on Statcast, because I prefer using exit velocity, it is simple, it is not an algorithm, and I will use exit velocity again later). Even in his slump, he has hit the ball hard with high enough frequency to remain dangerous at the plate.

While Polanco has still hit the ball hard, he has made one massive adjustment: he is trying to hit more home runs. With a 47.6% pull percentage and a 54.4% fly-ball percentage in 2018, Polanco has pulled the ball more than he ever has, but more notably, he has hit significantly more fly balls than he ever has. Polanco has never had a FB% above 38% in his career, and now he has the highest FB% in the majors. He has fully embraced the launch angle revolution, and it has worked somewhat; he has eight home runs and a 116 wRC+, meaning he has produced exceptionally well for the Pirates. But while he hits more fly balls, he also hits fewer line drives and grounders. Hitting fewer grounders works for someone like Gregory Polanco, but hitting fewer line drives harms his production.

PlayerFB%Average Exit Velocity (mph)
Gregory Polanco54.5%89.7
Leonys Martin53.7%89.1
Yoenis Cespedes52.8%90.6
Rhys Hoskins52.4%90.3
Joey Gallo52.2%94.2
Trevor Story51.5%91.3
Brandon Belt50%88.8


Of all the players with an FB% greater than 49.9%, Polanco has the third lowest. Gallo and Story, unsurprisingly, have hit more home runs than Polanco. Cespedes and Hoskins have hit the same number and fewer home runs than Polanco, but both have contributed more to their respective team’s offensive production. They also have .333 and .377 BABIPs, indicating they have received some luck. Martin and Belt, who have lower average exit velocities, have BABIPs of .340 and .366, respectively, showing they may have also received a bit of luck. But Polanco has a .242 BABIP and an xwOBA 33 points above his actual wOBA, indicating that he has received little luck this season. He will improve once more of those fly balls drop for hits, but fly balls lead to fewer hits than any other form of contact, apart from pop-ups. Furthermore, when Polanco had a similar exit velocity in 2016, he had his highest line drive rate, and he had his most productive season. Lowering his FB% to 45% and raising his LD% to 16 or 17% could make him someone who both hits for power and can reach base. He might even elevate himself from a good hitter to a dangerous hitter if he adds more line drives and base hits to his approach.


Gregory Polanco has made some adjustments at the plate. He is swinging less, but when he swings, he swings to put the ball in a crowd of people and not to find green outfield grass. Even in his cold streak, he has continued to hit the ball hard, so he can turn this season around. If he receives a little better luck, and he hits just a few more line drives, he could become one of the more productive hitters in the game. 

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