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 page or his FanGraphs profile or 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.

2010-2011: Starting strong

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, was recently listed for $25,999.99 on eBay.

2011-2012: Breaking through as a star

The big jump: Everything

How the card shows it: Everywhere

"I push myself. I see that people are saying I need to improve on this, I need to improve on that -- it's great. You take it to your heart and take it to your mind that you want to prove those people wrong and you want to do it." Mike Trout on setting goals

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.

2012-2013: Learning how to walk

The big jump: 4.08 P/PA in 2012, 4.21 P/PA in 2013

How the card shows it: 67 BB in 2012, 110 BB in 2013

"I got my little zone that I like. If the ball's not in that zone, I don't think it's a strike." Mike Trout on his approach

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.

2013-2014: Increasing power production

The big jump: .234 ISO in 2013, .274 ISO in 2014

How the card shows it: 27 HRs in 2013, 36 HRs in 2014

"I don't tell myself I want to hit home runs. Barreling up the ball and it going over the fence -- that's the biggest thing. If I try to hit a home run, I'm going to get out. There's times -- 3-1, 2-0 -- I try to take a hack, but I usually foul it back." Mike Trout on hitting home runs

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.

2014-2015: Crushing high fastballs

The big jump: .311 WOBA on upper-third fastballs in 2014, .466 WOBA on upper-third fastballs in 2015

How the card shows it: .561 SLG in 2014, .590 SLG in 2015

"I wouldn't say one particular thing helped with that. Putting it in the back of my mind, knowing they're going to try to get me out up there -- that's the biggest thing." Mike Trout on handling high heat

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.

2015-2016: Stealing bases again

The big jump: 3.0 BsR in 2015, 9.6 BsR in 2016

How the card shows it: 11 SB in 2015, 30 SB in 2016

"When you get your lead, when you're on first, if you're worried about maybe getting picked off instead of trying to steal that bag, you're never going to steal bags. I tell myself every time I get on first base, 'This guy ain't throwing me out.'" Mike Trout on stealing bases

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.

2016-2017: Getting even more patient

The big jump: swings on 23 percent of out-of-zone pitches in 2016, swings on 19.7 percent of out-of-zone pitches in 2017

How the card shows it: .991 OPS in 2016, 1.071 OPS in 2017

"My timing was on the majority of that season. When my timing gets off, that's when I start to chase. So I think just keeping my timing, that was the biggest thing for me." Mike Trout on not chasing pitches

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).

2017-2018: Going to the next level in center

The big jump: minus-6 DRS in 2017, 8 DRS in 2018

How the card shows it: 6.9 WAR in 2017, 9.8 WAR in 2018

"I still don't know how they calculate it, but knowing obviously 10 WAR is a great year, that's a goal, I think, for everybody. But I couldn't tell you what I need to do to get that up there." Mike Trout on WAR

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.

2018-2019: Can he cut down the K's?

The target: 124 SO in 2018

"Just being able to manage that two-strike approach. There's nasty pitchers in this game. They've got some good stuff. Sometimes they paint on you or something, and it's tough. But just cut the strikeouts down." Mike Trout on his 2019 goal

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.

More Mike Trout coverage: A $430 million bargain? | Why Trout can win a ring in Anaheim | Greatest ever? (ESPN+)