In early August, 2019 AL Rookie of the Year Yordan Alvarez was nearing a return to the Astros lineup, and Astros manager Dusty Baker faced a decision.

Josh Reddick or Kyle Tucker.

At that time, the answer wasn't clear. Statistically, Reddick was outperforming Tucker, Reddick had a more diverse batted ball profile that made him less predictable than Tucker, and Reddick provided more value defensively than Tucker. Aside from Tucker's lofty prospect billing, there really wasn't an objective reason for Tucker to play over Reddick.

Just shy of two months down the line, if faced with the same decision, the answer would clearly be Tucker, and it's not close. So what changed?

Image via: AT&T SportsNet/Screenshot.

On the left is an at-bat early in the season when the Dodgers came to Houston. The right hand side photo is from last week when the Diamondbacks came to town. As you can see, Tucker closed off his stance. It's crazy to think that this minute of a change can lead to such crazy results, but that's what happened.

Here is a swing against Diamondbacks starter Zac Gallen on August 6th. The offset camera angle makes Tucker's stance look a little more closed off than it really is, as this is the portion early in the year where he hadn't yet closed his stance off. Gallen throws an 83 MPH breaking ball on the outside part of the dish. It really isn't a great pitch, as it backs up on him a little bit and he hangs it, but Tucker blows out his front side, rendering him unable to do anything with that pitch other than foul it off and live to fight another day.

Now, here's an at bat against Gallen after Tucker adjusted his stance. This pitch is more center cut and hung even worse, but Tucker does something he was unable to do early in the year: drive it the other way. His closed off stance keeps his front hip from blowing out completely, and he stays on the ball and drives it down the line for a double. Notice how the ball is backspun down the line with true ball flight, not slicing, that shows just how well he drove it.

August 20th, the last game of the Seattle series before the Astros headed to Colorado, was the first time Tucker's stance was clearly closed off. Entering that game, Tucker was batting .192/.234/.329. He ended the season batting .268/.325/.512. That is quite the turnaround.

On August 6th, the day of that first swing against Gallen, Tucker had a hard hit % of 38.5%, a contact rate of 75.6%, a K% of 29.3%, and a BB% of 7.3%.

Tucker finished with a hard hit % of 44.5%. That 6% increase is the difference between the 45th percentile amongst hitters and the 78th percentile. Wow. Tucker also ended the year with a 79.5% contact percentage, a 4% increase. That significant increase helped him cut down on his strikeouts, as he ended the year with a 21.2% K%. His BB% stayed the same, as he ended at 7.1%, but three strikeouts for every walk is way better than four strikeouts for every walk.

All in all, the stance change gave Tucker more plate coverage. He still has the fast hands and instincts to react to pitches on the inner third, but instead of hooking them foul like he did, he's been keeping them fair. On top of that, Tucker now has plate coverage on the outer third of the plate, making him a more dangerous and consistent hitter. With one small change, Tucker went from a platoon bat, at best, to well above average amongst nearly every indicator of success.