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Logan Gilbert's Breakout Season

With the trade deadline in the rearview mirror, the Seattle Mariners currently hold onto one of three wild cards spots in the American League. While AL rookie of the year Julio Rodriguez has been the main event as the Mariners won fourteen straight before the all-star break, I want to bring some attention to the young starter who gave the Mariners something to be excited about before they flipped the switch in July.

Riding momentum from a promising debut in 2021, Logan Gilbert came out of the gates cruising with 3-0 record and 0.40 ERA in April, winning AL Pitcher of the Month. He has since cooled off (3.09 ERA, 1.18 WHIP, 8.4 K/9, as of time of writing), but has cemented himself as a staple in a strong rotation that now includes all-star Luis Castillo, as well as last season's AL Cy Young Award winner Robbie Ray. As the Mariners attempt to return to the playoffs for the first time in twenty years, I want to take a look at Gilbert's first half breakout campaign to give an idea of why he has been successful, but also identify some possible shortcomings that could come into play in the stretch run for Seattle.

The fifth pitcher selected in 2018 out of Stetson University, Gilbert cruised through the minors in 2019 with a 2.13 ERA, and after starting 2021 in Triple-A, he made 24 big league starts in his rookie year. He and Shane McClanahan have been the breakout stars of the 2018 draft class which also includes Casey Mize, Grayson Rodriguez, and Brady Singer.

Unlike any of the latter three, Gilbert has made an immediate impact for a winning ball club, and emerged as Seattle's most dependable arm in the first half of the season. In the below table, you will see the Mariners were 14-5 (.737 W%) in the games Gilbert started during the first half, compared to 37-36* (.507 W%) in games he does not, a whopping 23% increase in winning percentage with him on the bump.

Since the all-star break, Gilbert has turned in a pair of 6 IP, 2 ER starts against the Astros, and his first true bad outing of the year at Yankee Stadium. His start on Tuesday, August 2nd, (5.1 IP, 6 ER, 3 HR) ballooned Gilbert's ERA by 0.30 points, but up until that point, Gilbert had not allowed more than four earned runs in any of his starts in 2022.

Gilbert's dominance has a lot to do with the usage of his fastball. Averaging an electric 96 mph, it makes sense that Gilbert would throw it as often as he does (55.1% of the time). It's even more impressive when factoring in perceived velocity for his stride length, which gives a better idea of what hitters actually see due to Gilbert's 6'6" frame allowing him to get further down the mound. Gilbert's perceived fastball jumps almost two miles an hour to 97.9. Only Spencer Strider, Hunter Greene, and Shohei Ohtani have higher perceived fastball velocities according to Statcast, but all three of them throw at least 97 mph in unadjusted velocity.

For instance, in this at bat to well-known-baseball-masher Rafael Devers, Gilbert showed off for the gun and hit 99 mph, which to the hitter looks more like 101.

One other significant reason for Gilbert's breakout is that he changed-up the changeup (pun intended). Somehow Gilbert made an adjustment to throw it 6.3 mph harder (79.9 to 86.2), while also increasing its spin rate from 1555 to 1721 rpm. While whiff% for that pitch is down, BA against the changeup has decreased from .364 to .179, and SLG has seen a similar decline from an alarming .682 to an impressive .179.

So why might I be alarmed? The table below shows Gilbert's splits to righties and lefties based on how often he throws each pitch, and the slugging percentage to represent which situations hitters perform the most damage. For each individual pitch, Gilbert has worse is worse against righties, likely in part because he has a more limited arsenal. Against righties, Gilbert features a four pitch mix where he is fastball heavy, but mixes in each of the three off-speeds evenly, slightly favoring the changeup that moves down and away to lefties. However, against righties, he abandons the changeup, making up for it by throwing the slider more frequently. Logically, a hitter's job is a lot easier when he has to worry about four pitches compared to three, so it makes sense that righties get better results because they have a comparative advantage in the guessing game.

Additionally, while Gilbert accumulates a healthy number of strikeouts, he rates poorly in chase rate, suggesting he may be relying too much on blowing his fastball by hitters, like in this at bat to Trout. To his credit, Gilbert has done a good job limiting the long ball (only 16 so far, about 1 every 8 innings), but he is in the bottom 10% of the league in average exit velocity (91.5 MPH) and hard hit rate (46.7%). While he has avoided enough barrels, his success in avoiding the longball might be due to a lucky stretch, or even a result from the MLB changing its baseball for 2022 to be less lively. From the issues I have identified, Gilbert's weakness is power hitting righties, so it makes sense his worst outings have come to the likes of the Yankees, Blue Jays, and Phillies.

While Gilbert had a good ERA in the first half (2.77) , his xERA (4.15) was 1.38 points higher, the second biggest margin among qualified starters. The table below shows the ERA - xERA gap for all qualified starters in the first half (I listed the top 10 lowest and highest as well as all four Seattle starters). Derived by converting xwOBA to be uniform with standard ERA, xERA can be a useful tool to suggest possible flukes or lucky seasons, and vice versa. In other words, the pitchers with positive gaps were "unlucky," while the ones with red gaps were "lucky." Since Gilbert outperformed the projections derived using xERA, he might not be as lucky in the second half.

In his first season in the Seattle organization, Gilbert threw 135 innings, and after no season in 2020, Gilbert threw 124.1 innings in 2021. So far in 2022, Gilbert has accumulated 128.1IP, putting him on pace to shatter his career high at 195.0 projected innings pitched (12 expected starts x 6 IP average per game). There is no reason to imply he is on a pitch count, as pitchers naturally build up their tolerance and durability over their careers. However, as Gilbert will break his career record for innings pitched in 6.2 innings, his expectations should be adjusted as he pushes into uncharted territory for him.

Regardless of how well Gilbert performs for the rest of the season, he deserves a ton of credit for being a huge bright spot early in the season when there were not many in Seattle. The Mariner's magical run in early July makes it easy to forget the first three months of the season when they were not a very good team. Now riding the momentum after the long-win streak, Seattle can lean back into "America's Team" vibes. And now with Castillo in the fold, Gilbert no longer needs to be the ace. If Gilbert can eat up innings in the postseason push, he has enough help around him now where the Mariners have a good chance to break the streak, even if Gilbert does not keep up his elite first half pace. With the updated playoff format, manager Scott Servais has the luxury of three great options for a potential three game series, with Castillo, Ray, and Gilbert all projected to start in a Wild Card series.

In the big picture, Gilbert has the looks of a promising and durable starter for the next decade, regardless of how much he may regress in the second half. This is a guy who made it to the big leagues with only one year in the minors essentially, so for a first-round pick to pan out that quickly is a sign of excellent scouting and player development. With his high floor, Gilbert is a perfect playoff starter who can give five or six innings and limit opponents to a couple of runs. It is not that Gilbert's season has gone unnoticed, but he has flown under the radar in a crop of young American League starters, and if anything, this article is meant to give him some of the attention he deserves and give credit for keeping the pre-streak Mariners competitive. While I can pull up any advanced stat that might discredit Gilbert or depict him as a fluke, whenever he takes the mound with his large frame giving flashbacks to the first big unit that pitched in Seattle, hitters cannot deny how nasty Logan Gilbert is.

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