What the backs of Mike Trout's baseball cards tell us

The questions the past few days, in the wake of a $426.5 million extension that will span a dozen seasons, have centered on how long Mike Trout can maintain his level of greatness, whether he can provide the Los Angeles Angels with MVP-caliber performances into his 30s and, in a larger sense, whether he can extend his prime long enough to someday go down as the greatest ever.

Here's something that hasn't been considered: Mike Trout continuing to get better.

Take a close look at the back of Trout's baseball card -- or his Baseball-Reference pageor his FanGraphs profileor his ESPN section -- and you might notice the subtle, year-to-year improvements that define him as the player of his generation.

Trout, now embarking on his age-27 season, identifies an area to refine before reporting to camp every year, then spends his entire spring focused on it. It keeps him sharp and helps him stay motivated under circumstances in which most others would settle into contentment. And in the end, well, he gets better.

We took a look at the improvements Trout made each season and how he went about accomplishing them. We also identified what's next.

Trout didn't advance past Class A here, in his first year out of high school and his first full season as a professional baseball player. But he was already beginning to breeze through the Angels' system, setting the tone for what would become a sparkling career. The baseball card industry sees it that way, too. This card, in Gem Mint condition, wasrecently listed for $25,999.99 on eBay.

Everything

Everywhere

Trout began the 2012 season in Triple-A, which sounds crazy in hindsight but is actually quite reasonable if you consider the circumstances. The Angels' roster was littered with redundancies heading in, with three first basemen (Albert Pujols, Kendrys Morales, Mark Trumbo) and four established outfielders (Vernon Wells, Torii Hunter, Peter Bourjos and Bobby Abreu). Trout was sick for parts of that spring and battled a shoulder injury for the rest of it, limiting him to three games.

He was shipped to the minor leagues without complaint, then quickly forced his way to the majors by batting over .400 in the first month. The Angels released Abreu on April 27 in Cleveland, and Trout -- an inconsistent performer with sparse playing time in the second half of 2011 -- never looked back. He put together one of the greatest first seasons in history, winning the American League Rookie of the Year Award unanimously and nearly capturing an MVP at the age of 21.

Then came the hard part: Identifying areas to improve.

4.08 P/PA in 2012, 4.21 P/PA in 2013

67 BB in 2012, 110 BB in 2013

Trout took until he got a strike in the minor leagues. Now take a moment to think about how impressive that is: that a young player -- a teenager, actually -- who is still trying to figure himself out would possess the discipline to do such a thing. Voluntarily. Trout wanted to see as many pitches as possible, even if the first one happened to be a fastball right down the middle. He was so confident in his abilities that he didn't mind constantly falling behind in counts.

Members of the organization tried to dissuade him at certain points, but Trout never budged. He knew it would help. And did it ever. In 2013, Trout was coming off a historic rookie season, and the league had basically decided it was not going to let him beat it. Trout saw far fewer strikes, but he remained patient. That's why he was able to draw 43 more walks, representing baseball's second-largest increase in the past seven years. His on-base percentage rose from .399 to .432.

234 ISO in 2013, .274 ISO in 2014

27 HRs in 2013, 36 HRs in 2014

Trout tries his best to not chase home runs. He has learned his lesson from all those times when he found himself in favorable hitters' counts and wound up over-swinging. But he reached 36 home runs in 2014, his age-22 season, and so he took a run at 40 the following year and surpassed it, finishing with 41, which remains a career high. "It meant a lot," Trout said. "Obviously, you don't chase numbers throughout the season, but that was a cool accomplishment."

Home run power is actually the most surprising development in Trout's game. He always had the makings of a five-tool player, but he wasn't supposed to become such a prodigious home run hitter and certainly not one who would amass 240 in his first 1,065 games. Trout totaled only 23 in 290 career minor league games because he never had the prototypical home run swing. It was short and compact to the ball.

When he added the strength to complement his lightning-quick hands, the home runs followed.

.311 WOBA on upper-third fastballs in 2014, .466 WOBA on upper-third fastballs in 2015

.561 SLG in 2014, .590 SLG in 2015

In October 2014, with the Angels coming off an uplifting, 98-win regular season, a major flaw was exposed in Trout's game. While the entire nation watched, the Kansas City Royals constantly attacked him with chest-high fastballs, prompting a 1-for-12 showing in what ended in an American League Division Series sweep.

Trout had always been an exceptional low-ball hitter, but through 2014, he slugged only .254 on hard stuff in the upper third of the strike zone.

Trout entered the 2015 season focused on changing that. He worked on it in the batting cage, largely by setting up the tee as high as possible. But mostly, he continually reminded himself to look for pitches near his chest so he could react more quickly. That year, Trout slugged .453 on upper-third pitches. Suddenly the league didn't know where to pitch him.

3.0 BsR in 2015, 9.6 BsR in 2016

11 SB in 2015, 30 SB in 2016

It would've been easy for Trout to accept that he wasn't going to be a big base stealer any longer. It happened with so many other great ones -- Ken Griffey Jr., Andre Dawson, Willie Mays. Stealing bases takes a major toll on the body, and when the power emerges and hitters become a critical daily presence in their teams' lineups, taking an extra base becomes far less of a priority. Trout himself was settling into a noticeable pattern, with his stolen-base totals through his first four seasons going from 49 to 33 to 16 to 11.

Then he resolved to change that. When he reported to camp in 2016, Trout announced that he was going to get back to stealing bases. It became an area he paid more attention to than ever, reading pitcher tendencies on the rubber, practicing his first step toward second base and learning about pop times so he knew when it made the most sense to run. Trout wound up increasing his stolen-base total by 19. From 2014 to 2015, he averaged 14. From 2016 to 2018, he averaged 25, despite at one point missing seven weeks with an injured thumb.

swings on 23 percent of out-of-zone pitches in 2016, swings on 19.7 percent of out-of-zone pitches in 2017

The 2017 season marked the first time Trout dealt with a major injury, which is a shame because it was also a year when he was looking especially locked in offensively. By the time Trout tore the UCL on his left thumb while sliding into second base on May 28 in Miami, he held a 1.203 OPS that was on pace to be a career high.

Trout has never been one to chase; he has ranked within the top 13 percent in chase rates every season since 2013. But he took it to another level in 2017, chasing only 19.7 percent of pitches outside the strike zone. Only three players -- Joey Votto, Matt Carpenter and Tommy Pham -- did better. That helped Trout produce what remains the lowest strikeout rate of his career (17.8 percent).

minus-6 DRS in 2017, 8 DRS in 2018

6.9 WAR in 2017, 9.8 WAR in 2018

When Trout arrived at the Angels' spring training facility in 2018, he had a very specific request: to see the numbers. He wanted the front office to present him with the advanced analytics that painted him as a subpar defensive center fielder so he could pinpoint the areas to improve. Specifically, he wanted to compare his metrics to those of Jackie Bradley Jr., Kevin Kiermaier and Byron Buxton.

Among the 17 center fielders with enough innings to qualify in 2017, Trout ranked 13th in ultimate zone rating (minus-4.4), 12th in defensive runs saved (minus-6) and 13th in FanGraphs defense (minus-2.8). He spent the ensuing spring reading balls off the bat during batting practice on a daily basis and continued to work tirelessly on both his arm strength and his accuracy.

That led to significant improvements in all three of the aforementioned numbers -- 4.0 ultimate zone rating, 8 defensive runs saved, 5.8 FanGraphs defense -- and nearly won Trout his first Gold Glove.

124 SO in 2018

If you're looking for the one element of Trout's game that remains subpar, this is it. It isn't just Trout who strikes out a lot; it's the entire league. It's the launch-angle revolution and how much tougher it is to hit today's pitchers and the defensive shifts that have prompted teams to hardly ever sacrifice power to put balls in play. But Trout's strikeout totals are high even by today's standards.

He has collected 968 of them since his first full season in 2012, a mark topped by only seven other players. This year, strikeouts are the area that Trout will target. He has spoken about it at length with Albert Pujols, who in his prime was able to compile lots of walks without sacrificing any power and never striking out 100 times. It's the next obstacle -- perhaps the last one -- for Trout to conquer.

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