What Are the Reasons for Taijuan Walker’s Midseason Improvements?

After being terrible his first nine starts of the season, Taijuan Walker has been extremely effective in his last seven starts because of a decreased walk rate and increased groundball rate.

Taijuan Walker has been the epitome of Dr. Jekyll and Mr. Hide this season.

A lot of people bought into the Seattle Mariner after he had an absolutely dominant spring training. Those stats shouldn’t be given much weight, but that combined with his exceptional potential led to a huge surge in Walker supporters prior to the start of the 2015 season. A former first-round draft pick, Walker did not start the season off the way the Mariners or his fantasy owners expected.

The fantasy owners who believed in Walker -- and who invested quite a bit in acquiring him -- quickly diminished after he proved to be erratic and inconsistent through his first nine starts of the season. The only thing consistent about Walker was the fact that he would be inconsistent through each start.

In his first nine starts, Walker's stats by nearly every measure were disheartening, especially considering his expectations.

First 97.335.431.844.818.161.67

The numbers show that he was absolutely terrible and that was done with just a .356 batting average on balls in play, so he wasn’t extremely unlucky by any means, though that number was higher than the typical .300-or-so mark that pitchers can expect. The only bright side was his above-average strikeouts per nine innings, but it’s hard to use that as a building point when he had such a high walk rate.

After such a rough start to the season, Walker has finally lived up to the potential the Mariners and fantasy owners were expecting coming into the season. Walker has been nothing short of amazing since the end of May, and that can be attributed to his drastic improvement in his walk rate, an increased swing and miss rate, and an increased groundball rate.

Here’s his stat line through his last seven starts.

Last 71.682.630.790.569.50.93

This improvement is unparalleled in every aspect and helps support the notion that Walker is finally taking the necessary steps to establish himself as a young pitcher to be reckoned with.

Improved Command

Throughout his first nine starts, Walker was looking a lot like Ricky Vaughn from Major League before he got his glasses. Walker was walking way too many batters to help himself out, but he’s drastically improved his walk rate.

According to Fangraphs, Walker has also induced more swing and misses over his past seven starts compared to his first nine. He’s increased his percentage from 8.7% to 11.9%.

Here’s his pitch chart on swing and misses through his first nine starts (just click on them for a larger version).

Here’s his pitch chart on swing and misses through his last seven starts.

It’s interesting to see that he’s greatly increased his swinging strike rate on his split finger from 18.2% to 32.9%.

Batted Ball Improvement

With Walker’s extremely high fly ball percentage (50.0%) coupled with his inflated home run to fly ball ratio (HR/FB) of 14.5%, his early-season struggles make sense. He’s induced more ground balls lately, and that along with his drastically improved HR/FB ratio of 9.6% over his past seven starts has been a key to his turnaround.

Here’s a look at his improved batted ball percentages.

Last 741.6%16.8%41.6%
First 937.6%20.0%50.0%

He’s also found a way to improve the quality of contact as shown in the following table.

Soft %Med %Hard %
Last 719.1%57.1%23.8%
First 916.8%49.0%34.3%

These improvements on batted ball and quality of contact help explain why his numbers have greatly improved over the past month.

Pitch Usage

According to BaseballSavant, in his first nine starts, Walker’s usage rates on his two-seam and four-seam fastball were a combined 68.2% and his split finger changeup sat at 16.7%.

In his past seven starts, he’s slightly increased his fastball and split finger usage to 71.8% and 18.8%.

There haven’t been drastic changes in his pitch usage, but he’s obviously been more effective because he’s now inducing more groundballs and generating more swing and misses.

2015 Outlook

The main thing Walker needs to focus on controlling is his walk rate. The strikeouts will definitely be there with the exceptional pitching arsenal that he has, but his walk rate is something to keep an eye on throughout the rest of the season.

If Walker can maintain this recent success, then he’ll be on the road to dominance like other highly talented young pitchers such as Gerrit Cole and Chris Archer. There’s still a lot of room for improvement in Walker’s game, but this dominance may just be the beginning to an amazing career.