Hitting a baseball with authority is a very difficult sports thing to do. It is much harder than throwing/catching a football or scoring on a penalty kick or sinking a three pointer. However, there are many things a hitter can do to improve their chances of achieving offensive success in baseball. One such thing is to try and pull the baseball.
|MLB splits by batted ball direction since 2012
|% of PA
We can clearly see that hitters obtain vastly superior results when they successfully pull the ball. The MLB average slugging on pulled baseballs over the past four seasons is above 0.600 (for reference Nelson Cruz is slugging 0.590 in 2015) and a ball hit to the pull field is more than four times as likely to leave the yard for a home run as a ball hit to the opposite field. (Maybe this can help you better understand why some players refuse to simply lay down a bunt when their opponents employ a heavy defensive shift against them?)
Lots of hitters are good at roping meatballs into the pull field for extra bases. However, one hitter who is particularly good at this plays at the Hawt Corner for your Seattle Mariners. To obtain some perspective re: Seager's pull prowess, we can compare him to the very best hitter is in all of baseball: Miguel Cabrera.
|Statistics for balls hit to the pull field (since 2012 - Kyle's first full year in MLB)
Since 2012, Miguel Cabrera leads all of baseball in both batting average and slugging percentage. His wRC+ of 168 is second best over this period (just behind Mike Trout's 169). During these four seasons, Miguel Cabrera won two MVP awards and a triple crown. It should also be noted that Cabrera hits at his very best when pulling the baseball (his career wRC+ when pulling the ball is more than 60 points higher than when he goes to center or to the opposite field). However, despite all of this success, Sweet Kyle Seager is still better at pulling the ball than Miggy is. This is a crazy thing.
Cabrera, of course, is a much better overall hitter than Kyle. His ability to punish the ball to all fields is amazing.
Here are all of the extra base hits that these gentleman have slugged since the beginning of the 2012 season. The balance showed by Miguel Cabrera suggests a generational talent. (It's no surprise that of the 968 players in MLB history with 5000+ PA, only 20 have a higher wRC+ than Miggy.) Alternatively, although Kyle has been able to sneak some doubles down the left field line, he only has a handful of home runs to left or center field. His seeming inability to consistently use the middle and opposite fields is what's currently preventing him from being a great hitter.
However, over the last few seasons, Kyle has shown an increased ability to successfully use the middle of the field. He's also demonstrated that he's not afraid/too proud to drop down a bunt against the shift when the M's need a baserunner. But as teams continue to shift more aggressively against him, it'll likely be important that he tweaks his approach in order to find continued success. It's understandable that he might be a little reluctant to change his game plan too much because he's been excellent at pulling the ball, but his pull numbers the last few seasons have dipped from "WHAT, WOW, SO GOOD" to "This is very, very good". Excelling in baseball relies heavily on one's ability to continue to adapt and evolve and out-think the opposition. You can do it, Kyle. Keep up the good work.