top of page

MLB Power increases: A Research Project

A couple weeks ago, I was looking at Sammy Sosa's massive improvement in home run output from 1996 to 1998. A a part of that article, I brought up Christian Yelich and Javy Baez as comparisons for other players who experienced surprising booms in power. I I started researching numbers and generated a huge chart to help plot some interesting seasons and statistics.

My chart is designed to find interesting increases in power. Both in a sense of how star players led into some of their best seasons, as well as trying to find some outlier players who experienced a sudden and surprising increase in power. There's going to be a couple longtime sluggers in there, as well as some one off surprise seasons. My chart isn't designed to draw specific conclusions like finding evidence that certain players were cheating. Nor was it to find overall trends in power. It's basically to find surprising increases in power, and compare them to contemporaries so you see just how historical some of these numbers are.

The stats I used:

-Year 1/Year 2: So you know exactly what years these seasons took place. All seasons are sequential, showing annual improvements

-Age, from year one. Allows you to see when most of these guys unlock their power. Is it in their 20s as they figure out the game? Or are some of these guys strapping it on later in their careers?

-HR: The home run totals from that year

-HR%: Percentage of plate appearances where a home run is hit. Not at bats. so if a player has a 5% home run %, that means they are hitting a home run 5% of the time they come up to bat.

-HR/FB: % of outfield hits that were home runs. Includes fly balls and line drives. Essentially measuring how many home runs were hit based off of deep contact. a 25% HR/FB means that one quarter of all hits going to the outfield will leave the park.

-SLG: Slugging percentage, total bases/At bats. Just so you get a feel for what their production was like, year over year. Some guys would hit a lot of doubles, then those doubles would start leaving the yard. Other guys would discover power and go to just hitting home runs.

A couple of notes before we jump in:

-HR/FB% was a statistic that was unavailable before 1988.

-For each category, I've put in bold the leader of that statistic, based off the column.

-Most players are going to be from the last 10 years, especially the last 5.

-I did include a couple of historical examples (Babe Ruth, Roger Maris, and George Foster), as well as a bunch of players from the steroid era.

-I limited myself to 50 players. It's a nice round number that allowed me to get most interesting cases. I'm sure I missed a few interesting seasons here and there. Feel free to comment and let me know what I did miss.

-I tried to include all the big home run seasons, so you'd get a feel for what some of these numbers look like at their absolute best, or essentially, what the high end of the scale looks like. A .600 SLG might seem Ruthian, until you see that he slugged .690 for his career.

-I included a couple players who had major increases in slugging, not just home runs. Again so you'd get a couple more controlled variables.

-I typically didn't include consistent power hitters like Hank Aaron. They just didn't seem relevant towards what I was doing, since they didn't have the same massive spikes in production I was looking for. Some of these guys will seem like consistent power hitters, but I handpicked them because they had single seasons where they went off away from their career trends. Aaron would average between 30-45 home runs like clockwork. McGwire would have 30 one year, then 50+ another.

-I did not include players who had major home run increases that were in direct correlation of how many games they played. Jorge Soler just jumped from 9 home runs in 2018 to 48 in 2019, but he's not on my list because he went from 61 games played to a full 162. All of the players on the below list will have played at least 3/4ths of a season to qualify.

-Barry Bonds is the only player on my list twice. He had two years of back to back growth, and I felt like I needed to include both rather than choose between. So technically my list is 49 players.

A couple of highlights from the chart:

-Average starting home runs was 27, and everage ending home runs was 45.

-Average starting HR % was 4.7%, ending 6.8% for a 2.1% increase.

-Average starting HR/FB was 13.5%, ending was 18.9%, for a 5.4% increase.

-12/50 seasons were by age 30 or older players, just to show you how low rate that is. Average age for a starting season was 27.5.

-Bryce Harper owns the single biggest increase in SLG on the chart, going into his MVP 2015

-The largest HR/FB % was Mark McGwire in 1998, a whopping 31%

-The biggest increases in HR rate include Jose Bautista's age 29 2010, JD Martinez's age 29 2017, Brady Anderson's age 32 1996.

-There were 5 players who had a jump of over 10% in their home run fly ball percentage: Brady Anderson 1996, Jose Bautista 2010, JD Martinez 2017, Jose Altuve 2019, and Barry Bonds 2001. Just missing was Luis Gonzalez 2001, as he went from 32 to 57 home runs, and a 9.6% HR/FB increase

-15 players increased their home runs by 3% year over year (including a handful of 2.9% rounded ups)

-4 players actually experienced decreased slugging, despite increased home runs: Ronald Acuna, Albert Belle, Mo Vaughn, and Jose Ramirez. I'm not sure how that happens.

The Players and Seasons

Babe Ruth: So Ruth is obviously the great power hitter of all time. He had some peaks into higher single season home run totals previously, but had his big 1927 at age 32.

Roger Maris: Maris was only 26 when he caught Ruth. He was a solid power hitter, having a career year.

Barry Bonds: Had a down age 34 season, then major increases for the next two years as he went Ruthian. It was a late surge, although he had had great seasons nearly 10 years prior for Pittsburg.

Mark McGwire: An example of a more consistent power hitter. I chose his lead in 1997 to his record setting 1998.

Sammy Sosa: As I previously wrote about, Sammy had a down 1997 before spiking in 1998. He had a fairly big year over year jump, because of this.

Brady Anderson: Arguably one of the more mysterious outlier years. huge increases never to be seen again.

Luis Gonzalez: Another mysterious outlier year, as he went from a 30 HR per year hitter to a major spike.

Andruw Jones: A consistent 30 HR power hitter who had a career year.

Ken Griffey Jr.: Junior was a solid up and coming power hitter before he made improvements and hit next level status at just age 23.

Albert Belle: A longtime power hitter who had a couple big years. An example of good becoming great.

George Foster: His 52 home run 1977 always stood out to me as an outlier. He'd have 2 other solid HR years after it.

Alex Rodriguez: Arod was a solid consistent home run hitter. After a slightly subpar 2006, he went off at age 31 for one of his best seasons of his career.

Greg Vaughn: Another longtime big bopper who discovered a new level of power at age 30.

Chipper Jones: An example of a good hitter becoming great as he enters his prime and discovers new power.

Rafael Palmeiro: A guy who discovered an entirely new level of power at age 29.

Jay Buhner: Buhner went from a home run hitter in the 20s to a 40 per year guy.

Richie Sexson: An early 2000s guy who found new power as he went into a typical prime.

Andres Galarraga: Had one of the latest power increases on the list, at age 35. Suspiciously old and in his 4th year at Colorado when he discovered the power stroke.

Mo Vaughn: A big guy who hit 40 home runs for several years, this being the lead in.

Lance Berkman: Berkman was one of those guys often thought of as a huge power hitter, but only had two great seasons. 2006 being one of them.

Jose Canseco: He had several big power years, but none as unlikely as his late 1998 power run. Highly suspicious.

Carlos Delgado: At age 31, he discovered new power levels that he hadn't quite achieved before. A late bloomer for sure.

Christian Yelich: Yelich went from a decent hitter in Miami to a top HR hitter in Milwaukee.

Jose Bautista: Joey Bat's first big season led into several others. As a late bloomer, his level of improvement was among the highest on my chart.

Chris Davis: Another stereotypical home run hitter who came into his own.

Matt Kemp: Onetime Dodgers stud who had some pop, but then was able to kick it up a notch.

Adrian Beltre: Had his career year where his power topped out at levels that would not be seen again.

Mark Trumbo: Another stereotypical slugger who increased his homer total by 25 at age 30

Chris Carter: A guy who had his best year at age 29 for the Milwaukee Brewers. A one year wonder.

Josh Donaldson: A late bloomer hitter who came into his own at age 29.

Jose Ramirez: Indians infielder with some pop, even though he's leveled off since then.

Brian Dozier: Another guy with decent power who put it all together and had a bump in production.

Victor Martinez: A guy who was always a good hitter, but developed elite power at age 35. A very interesting late bloomer

JD Martinez: This guy is among the tops on my list for increases. He jumped by 23 HRs, a whopping 5% increase, and largely due to his increased HR/FB rate of 13.5%, all at the age of 29

Justin Smoak: Another stereotypical slugger who came into his own late.

Logan Morrison: Among the league leaders in home runs for 2017. A guy who's been ravished by injuries, but put it all together in a big way.

Edwin Encarnacion: Another masher who increased his homer totals in a big way.

Nelson Cruz: A guy who's been around forever, but didn't become a big bopper until age 33

Mookie Betts: A look at him coming into his MVP season, as he greatly developed his overall power game. 2nd highest SLG increase on my list.

Jose Altuve: He was a decent power hitter for a couple years. His power took a step back in 2018, then rebounded in a major way in 2019. His two best power years were 2017 and 2019.

Khris Davis: Another guy who figured out pop at age 29.

Eugenio Suarez: A decent hitter, who hit nearly 50 home runs.

Alex Bregman: A younger guy who posted an odd increase in homers without increasing his HR/FB rate.

Ronald Acuna: A bit of a younger guy on the list. I wanted to include him so you could see how rare it is to have such power from such a young player.

Javy Baez: A free swinger who put it together with a better approach as he matured.

Kyle Schwarber: A younger slugger who's shown reasonable improvement as he's gotten a few years older

Francisco Lindor: Another guy who had pop but discovered a new level of it as he matured.

Bryce Harper: A guy who had a huge increase in slugging, while not hitting video game level home run numbers.

Mike Trout: Trout's always been a consistent power hitter, but discovered next level power for the last 3 years. His two seasons show the before and after.

Who did I forget? What trends did I fail to notice?


Recent Posts

See All


bottom of page