What Happened to Mason Thompson?

Washington Nationals v Minnesota Twins
Washington Nationals v Minnesota Twins / David Berding/GettyImages

Historically, the Nationals bullpen has always had a flair for the dramatic. Over the years, the Nats postseason contending teams have been hampered by their various bullpen groups have been consistently inconsistent and often otherwise troublesome. You may recall the Jonathan Papelbon Incident, the Shawn Kelley Incident, various Drew Storen meltdowns, and more. There's always something going on with the relievers on this team, so this question won't be unfamiliar to Nats fans.

Is Mason Thompson Broken?

Mason Thompson is a 25-year-old right hander in his third year of his MLB career. He represents a good bit of business for the Nationals by contributing in the major leagues at all, considering how the team acquired him. At the trade deadline in 2021, the Nationals traded World Series hero Daniel Hudson to the Padres for Thompson and Jordy Barley. Getting any two prospects for a 34-year-old reliever on an expiring contract is generally worthwhile for a noncompetitive team, and Thompson has certainly flashed some high level potential that any team would surely exchange 19 innings of Hudson for.

So, how good is Thompson now, and how good can he be? Like many hard-throwing young relievers who are converted from being starting pitchers, Thompson has had issues staying healthy in his young career. Thompson has only surpassed 30 innings pitched once in 7 professional seasons, when he had 93 innings at A-ball at age 20. So far this year, he is 2.1 innings pitched away from a career-high in MLB, and it's the middle of May. We can't accurately determine how good a pitcher is with such a small sample; Thompson staying on the mound for most of the year this season and in his next couple of seasons is priority number one for him and the Nats.

The story for Thompson this season is an up-and-down one: the up part being his first ten games, the down part being his last six. From his first appearance on March 30 up to April 25, Thompson had an ERA of 0.96 over 18.2 innings. Seven of those ten appearances were for more than one inning, and Thompson quickly became more trusted in high-leverage spots by the end of April. He picked up two wins and a three-inning save, allowing just two earned runs, striking out 17, and walking just one batter. At that point, Thompson seemed like he was experiencing a certified reliever breakout and fans were wondering whether he would soon become the team's closer or the otherwise most-trusted reliever.

Unfortunately that kind of hot streak pretty much never lasts (unless you're a reliever that the Nationals traded to the Athletics). Thompson has followed his terrific start by allowing runs in five of his six most recent outings, notching two blown saves and a loss with a 22.09 ERA in that span. It was two days after his 28-pitch, 3-inning save against the Mets on April 25th when he suddenly began struggling. It's possible that a long string of multi-inning appearances drained Thompson's energy, and he now has looked unreliable on the mound. He has failed to retire even three batters in four of his last six games and his season stats have fallen off significantly. Through April, Thompson was on pace for over 90 appearances - a clear sign of overuse.

So far this year, Thompson's biggest strength has been avoiding hard contact. He is in the 93rd percentile in average exit velocity against per Baseball Savant and has only allowed two home runs. In addition, he has walked about two hitters per nine innings, which is a very solid rate that was even better before his last couple of outings. With good command and stuff that is hard to square up, Thompson already has the perfect blueprint to be an above-average reliever, even with a slightly underwhelming strikeout rate.

Thompson relies heavily on his fastball: a hard two-seamer that averages 94 miles per hour that he uses 68% of the time. The pitch is almost exclusively paired with a standard slider with vertical movement that Thompson has found most of his success with. Thompson has allowed just two hits off of his slider and none off of his much less-used curveball, but the bad results have come off of his fastball which has allowed a hard hit rate north of 40%. The key for Thompson is commanding his slider inside and outside of the strike zone, and an increase in slider usage would be a great way for Thompson to improve if he can throw it consistently.

Problems can arise quickly for Thompson as a two-pitch pitcher with only one of those pitches having above-average stuff. If Thompson cannot locate the slider, hitters can sit on a hittable fastball and he runs into trouble. Even when Thompson was going good early this year, his control was not always perfect. He seems to throw a high number of waste pitches and find the center of the zone a little too often. He is still able to avoid walks thanks to his fastball-heavy profile, but it's not a good enough fastball to survive by just pumping it in the zone over and over. To get out of his current slump, Thompson needs to be able to locate both of his pitches to get whiffs and soft contact.

The margins of performance are incredibly slim for relief pitchers like Mason Thompson. The smallest variations in pitch location can lead a pitcher from being dominant to getting crushed by major league hitters. Even without variations in performance, it's hard to draw conclusions that actually stick in just a month or two of work out of the bullpen. After ten games, Nats fans saw a closer in Mason Thompson, and just a few weeks later everyone's minds have been changed. There's no real reason to panic: at least Thompson is healthy. He will get the chance to get back on track and fine tune his arsenal, and we will be able to watch the next few years of Thompson as he hopefully blossoms into a top-end bullpen contributor.

Whether or not Thompson has more struggles this year he's already a success story for the Nats organization. The real deciding factor will be how Thompson is managed by Nats coaches and by Davey Martinez. It's up to Davey to work with Mason and determine the best usage for the young righty. It's possible that he's a better fit in one-inning outings, but the potential of a multi-inning ace reliever should not be discarded as it can be highly valuable and can coax extra innings of work out of one of your best arms. There's no perfect way to tell what the best route is for Thompson from the outside, so it's on the Nats to optimize his usage. It's only May, so most things are too early to call, but I can say this: no, he's not broken, at least not yet.