MLB's most consistent hitter? Corey's brother

"Consistent" is a commonly used compliment in the baseball world, but rarely is consistency actually measured or recognized.
Of course, consistency only matters if a player is consistently good, but those who fit that description offer their teams a reliable producer who can be counted on to perform every year. That's enormously valuable, even for a player whose ceiling might not be as high as some others.
But who is the most consistent hitter in the Majors?
There isn't one, perfectly scientific way to answer this question. We can take a shot at it, however, using a step-by-step process to evaluate over the past five years (2013-17).
Step 1: Staying power
A key piece of providing consistent production is having the opportunity to do so. That means earning play time, but also staying healthy over the course of a grueling 162-game season, year after year. Easier said than done.
A player who hits up high in a good lineup -- say, Francisco Lindor in 2017 -- can accrue more than 700 plate appearances. But 500 is roughly the number a hitter needs to qualify for the batting title, so that seems like the best baseline in this case. So we'll start here with the hitters who have accrued at least 500 plate appearances in each of the last five seasons.
Results: 31 hitters
Jose Altuve, Elvis Andrus, José Bautista, Jay Bruce, Asdrúbal Cabrera, Miguel Cabrera, Robinson Canó, Matt Carpenter, Brandon Crawford, Chris Davis, Brian Dozier, Edwin Encarnación, Alcides Escobar, Todd Frazier, Brett Gardner, Chase Headley, Eric Hosmer, Adam Jones, Ian Kinsler, Evan Longoria, Nick Markakis, Joe Mauer, Andrew McCutchen, Daniel Murphy, Buster Posey, Anthony Rizzo, Carlos Santana, Kyle Seager, Jean Segura, Mike Trout, Justin Upton
Step 2: Production
Staying in the lineup is great, but again, the goal of this exercise isn't just to find a consistent hitter, but a consistently good one. Therefore, it's necessary to chop down the initial list to isolate the most productive bats.
OPS+ provides an easy way to do that, adjusting a player's raw OPS for park factors and the league's offensive environment, then putting it on a scale where 100 is average, and the higher number the better. (Trout led qualified hitters with a 187 OPS+ in 2017, meaning his adjusted OPS was 87 percent better than average.) So let's take those 31 hitters and pick out those who have posted at least a 100 OPS+ in each of those five seasons.

Results: 12 hitters
Cano, Carpenter, Encarnacion, Longoria, McCutchen, Murphy, Posey, Rizzo, Santana, Seager, Trout, Upton
This is an impressive list that includes the best player in the game (Trout) and two other MVP Award winners (McCutchen, Posey). That only a dozen men have reached both the 500-PA and 100-OPS+ marks in five consecutive seasons speaks to just how difficult it is to consistently provide quantity and quality at the plate over the long run in MLB. That helps explain why the Phillies were so aggressive in bringing in Santana.

Step 3: The "range factor"
Again, the target here is consistency. So while we wanted hitters who are above average each year, we also can get more precise than that by considering their range of outcomes. Therefore, this step will involve cutting the list in half to include those with the smallest gaps between their highest and lowest OPS+ during that five-year span.
Results: Six hitters
Trout: 19 points (168-187)
Encarnacion: 24 points (128-152)
Seager: 26 points (107-133)
Posey: 28 points (115-143)
Carpenter: 28 points (112-140)
Upton: 29 points (106-135)
This eliminates hitters whose production has either dramatically fallen off (such as McCutchen) or taken off (such as Murphy) of late. It leaves six consistent bats, whether they belong to a once-in-a-generation superstar such as Trout, or a more quiet, under-the-radar performer such as Seager.
Step 4: Power play
Home runs are a major part of the game today, so it would seem like an oversight not to factor them into this process in some way. The prevalence of power has changed considerably in the short time period being considered here -- there were nearly 2,000 more homers MLB-wide in 2017 than in '14 -- but even in '14, there were nearly 60 players who popped 20 or more big flies. That's where we will set the yearly minimum for this group.

Results: Four hitters
Encarnacion: 189 total HR (range of 34-42)
Upton: 148 total HR (range of 26-35)
Trout: 166 total HR (range of 27-41)
Seager: 130 total HR (range of 22-30)
Playing in San Francisco, Posey has reached the 20-homer mark once in the past five years (22 in 2014), and he hit only 12 in '17. Carpenter has popped 20 or more roundtrippers for three straight seasons, but only after going deep a combined 19 times from 2013-14.
Step 5: Total it up
As the foundation of slugging percentage, the total bases stat is a bit of a blunt instrument, but in this case it's a useful one. To accrue a lot of total bases, a player needs to stay on the field, produce and have pop in his bat -- basically all of the ingredients that have contributed to this process.
Our four remaining players are among the 26 hitters to collect at least 200 total bases in five straight seasons, and among the nine to reach the 240 mark (also Cano, Jones, Longoria, McCutchen and Rizzo). But again, in the name of consistency, we'll sort the final quartet by the smallest range between the player's highest and lowest total.
Results
Seager: 38 TB (260-298)
Upton: 55 TB (246-301)
Encarnacion: 57 TB (261-318)
Trout: 86 TB (253-339)
Winner: Seager
First, let's give the honorable mentions their due. A late bloomer, Encarnacion finally busted out at age 29 in 2012, and since then has been a terrifying force at the plate every year while leading the Majors with 231 homers. In contrast, Upton was a two-time All-Star by age 23 and has produced at least 571 plate appearances and a 106 OPS+ for nine consecutive years.
And then there's Upton's teammate, Trout, who amazingly enough might have come out on top in this exercise if not for last year's thumb injury. Although Trout just managed to clear the 500-PA plateau, his lack of playing time held him to 49 fewer total bases than in any other full season. Still, Trout's six seasons of at least 500 PA and a 165 OPS+ since 2012 tie Ty Cobb's record for any player through his age-25 campaign.
But it's the man now known to many as "Corey's brother" who is our "Mr. Consistent." Following a 53-game debut with the Mariners in 2011, the elder Seager has been a metronomic fixture in the Seattle lineup over the past six seasons. The 30-year-old has logged at least 154 games in each of those years, providing minimums of 27 doubles, 20 homers and a 107 OPS+, all while playing a strong third base.

So while Seager might not be as big of a star as his younger sibling, he is, by this measure, the most consistent hitter in the Majors.