One way to track the potential of a young star becoming a power hitter in the major leagues is to monitor doubles hit through their minor league career.
Let's start with a couple of elite players - Trea Turner and Anthony Rendon - and their minor league statistics.
Turner spent 69 games in the minors in 2014 and hit 16 doubles, which is one double every 4.3 games. That number stayed about the same in 2015, when Turner hit 24 doubles in 116 games, which was one double every 4.8 games. Turner hit five homers in the minors in 2014, and eight round-trippers in 2015.
But when he became an everyday major league player, Turner's home run totals gradually went up as he continued to get better as a hitter. From 2016 to 2020, Turner's home run totals per season were: 13, 11, 19, 19 and 12. His HR%, or percentage if all plate appearances he hit a home run, went up from 2017 to 2020: from 2.5 to 2.6 to 3.3 to 4.6. With 12 homers in the abbreviated 2020 campaign, Turner hit a homer a every 5.7 games, a career best.
Turner played in 185 minor league games, while former Nationals third baseman Rendon managed only 79 minor league games before being called up for good to the major leagues. In those two minor league seasons, Rendon demonstrated his ability to see pitching and get better each year. In 2012 in 43 minor league games, Rendon hit a double every 5.4 games. In 2013, he hit a double every 3.0 games - or four more doubles (12 to eight) in seven fewer games.
Rendon was always known for his ability to hit doubles while playing in D.C., and he was affectionately known as "Tony Two Bags" by Washington faithful every time he would lace a double to the gap. In his last three seasons with the Nats, from 2017 to 2019, Rendon ripped over 40 doubles each year: 41, 44 and 44, all-career highs.
With that, his best home run totals went up pretty much every season from 2016 to 2019: 20, 25, 24, 34. His HR% rose from 4.1 to 5.3 in the three campaigns with the Nats. Rendon his a career-best home run every 16 at-bats with the Nats in 2019.
So one can see how doubles can turn into home runs once a good hitter gets consistent enough at the plate. Inevitably, when reporters ask a player how he hit the home run in a crucial moment in the game, the player will respond with something along the lines of: "I was just trying to make good contact" or "I just barreled up that ball." You will never hear a good hitter say, "Oh, I was just trying to get the ball up in the air." No, the home runs come because it is a good hitter making good contact.
Looking into the crystal ball of some of the younger Nats prospects that got their feet wet in the big league pool in 2020, there are some promising doubles numbers, too.
Infielder Luis GarcÃa hit eight, 21 and 22 doubles in his three seasons in the minors from 2017 to 2019. Garcia hit a double every 6.1 games in 2017 and improved that to 5.9 in 2019.
Outfielder Andrew Stevenson looked the part of a player that was hot in 15 games with the Nats in 2020. Stevenson had hit five doubles in 124 big league games from 2017 to 2019. But in nearly three weeks with the Nats to end this season in late September, Stevenson hit a career-high seven doubles in just 41 at-bats. Stevenson started his minor league career in 2015 by hitting a double every 13.8 at-bats. In 2019 minor league play, Stevenson cranked out 21 doubles in 93 games, or one every 4.4 games, a career high.
Is the trend for doubles to turn into homers predicative for every potential power hitter in the big leagues? Of course not. But it is interesting to see how these trends worked out for elite hitters like Turner and Rendon. And it certainly bodes well for a player like Stevenson, who showed off a good eye and quick hands with the Nats in 2020 to the tune of 10 extra-base hits and a career-high .732 slugging percentage, albeit in a small sample size.