Mookie Who? Tyler O’Neill Is the Hottest Hitter in Baseball

Tyler O’Neill didn’t take long to adapt to a new team. Traded to the Red Sox in December after spending six years with the Cardinals, O’Neill claimed sole possession of a major league record by homering on Opening Day for the fifth straight season. As we approach the two-week mark of the season — yes, it’s early — he finds himself atop major leaderboards and has helped Boston get off to a 7-4 start.

On Tuesday at Fenway Park, O’Neill launched a towering solo shot over the Green Monster off Orioles ace Corbin Burnes to put the Red Sox up 1-0 in the first inning:

The Statcast-estimated distance of 413 feet made that O’Neill’s longest of this season so far. It was his sixth homer, momentarily moving him out of a tie with Mookie Betts, Marcell Ozuna, and Mike Trout, though Trout countered with his sixth later on Tuesday night. Nonetheless, O’Neill has matched Fred Lynn’s hot 1979 start for the most homers by a Red Sox player in the team’s first 11 games of a season, doing so while making just nine starts and a pinch-hitting appearance. By comparison, last season O’Neill didn’t hit his sixth home run until August 11, and finished with just nine in 72 games.

O’Neill began the season by homering off Mariners reliever Cody Bolton on Opening Day in Seattle. In doing so, he broke a tie with Yogi Berra (1955–58), Gary Carter (1977–80) and Todd Hundley (1994–97) for the most consecutive Opening Day games with a home run. (And you thought you were glad baseball was back!) He closed out the Seattle series with a homer off Bryce Miller on March 31, took the Angels’ Griffin Canning and José Soriano deep on April 5, then added a dinger against Chase Silseth on April 7.

Unfortunately for the Red Sox, O’Neill’s blast on Tuesday was their only run of the day; they lost 7-1. And oddly enough, the 28-year-old left fielder hasn’t driven in anyone else despite his six home runs, which is more a commentary on his teammates than his own failings; he’s 1-for-3 with a pair of walks with runners in scoring position. Regardless of his RBI total, he’s swinging a very hot bat overall, hitting .344/.488/.906. It’s not every day you’re miles ahead of two future Hall of Famers for the major league lead in key categories, so we’ll note that his slugging percentage is 126 points ahead of the second-ranked Trout, and his 276 wRC+ is 32 points ahead of the second-ranked Betts. Meanwhile his on-base percentage merely leads the American League.

Of course, O’Neill has played just 10 games, the first nine of them against the Mariners, A’s, and Angels — all on the road — and there’s only so much we can take from that, but the number one thing is that he’s healthy, and that’s a big one, because save for his monster 2021 season and his brawny physique (“listed at 5-foot-11 and 200 pounds, of which about 198 pounds is biceps and quads,” wrote Michael Baumann), injuries have largely defined his career.

Drafted by the Mariners out of a British Columbia high school in the third round in 2013, O’Neill became a Cardinal in the Marco Gonzales trade four years later. He debuted in the majors on April 19, 2018, but spent much of that season and the next one bouncing back and forth between Triple-A and the majors, with five (!) trips to the injured list thrown in for good measure. After spending all of 2020 in the majors and on the active roster — and even winning his first Gold Glove, but hitting a miserable .173/.261/.360 — he finally got something close to a full-length season under his belt in 2021, hitting .286/.352/560 (143 wRC+) with 34 homers, 15 steals, and 5.3 WAR in just 136 games, but accompanying that with two more trips to the IL. He added a second Gold Glove that year, and finished eighth in the NL MVP voting, but since then he hasn’t come close to replicating that season, with injuries limiting him to just 168 games, 23 homers, a 98 wRC+ and 2.0 WAR across 2022–23, another two-year span that included five trips to the IL:

Thus the 28-year-old O’Neill entered this season having played more than 100 games in a major league season just once, and more than 72 just twice. Between his injuries, a crowded field of alternatives, his increasing price tag, and a spat with manager Oliver Marmol — who publicly questioned O’Neill’s effort running the bases during a heavy rain last April 4 in St. Louis, calling his effort “unacceptable” — O’Neill fell out of favor in St. Louis. On December 8, the Cardinals traded the pending free agent to the Red Sox in exchange for a pair of righty relievers, Nick Robertson and Victor Santos.

So far, the change of scenery seems to agree with him, though it’s worth noting that Tuesday’s game was his first at Fenway with the Red Sox. One game, one homer? That’s a pretty good rate!

In light of O’Neill’s long history of leg woes, it’s worth pointing out that as of now he’s hitting the ball harder than in the past two seasons. I present these stats while acknowledging that we don’t have enough data to draw strong conclusions about what’s happening yet; this is as much about his decline from 2021 as it is his torrid start:

Bear in mind that, as Baseball Prospectus’ Russell Carlton has noted, exit velocity stabilizes around 40 batted ball events, and barrel rate at 50 BBE, while groundball, fly ball, and hard-hit rates do so at 80 BBE. Within this small sample, this year’s exit velo and barrel rate at least look more like 2021 than ’22 or ’23. On a rolling basis of 25 plate appearances, both his xSLG and xwOBA show that his season-opening hot streak resembles only two or three stretches from the past two seasons, while he had a handful of such stretches in 2021:

The other thing to note about O’Neill is how much he’s tightened his approach so far. He’s a guy with a lot of swing-and-miss in his game, so much so that even as he ranked no. 61 on our Top 100 Prospects list in 2018, he had 30/40 grades (present/future) on his hit tool, and from 2018–23, he struck out 30% of the time, seventh among hitters with at least 1,500 PA in that span. Production-wise, he’s near the upper end among guys with strikeout rates in that neighborhood; of the hitters with the 30 highest strikeout rates over at least 1,000 PA within that span — everybody from 28.8% up — his 111 wRC+ ranks fourth, behind only Luke Voit (123), Giancarlo Stanton (122), and Teoscar Hernández (117).

Entering this season, O’Neill had swung at 72.5% of pitches within the strike zone, including 71% last year; so far this year, he’s cut that down to 50.8%. Similarly, his overall swing rate of 48.1% entering this year (44.9% last year) is down to 36%. His swinging strike rate of 15.4% (11.2% last year) is way down to 6.4%, and his strikeout rate, which was 25.2% last year, is at 19.5%. Mind you, none of these stats have stabilized — swing rate takes about 50 PA (he’s at 41) and strikeout rate requires roughly 60 PA — but those are at least promising trends.

We’re obviously still early enough in the season that any trend could be a mirage, a two-week heater or skid that might not merit closer scrutiny if it were located in mid-June or the dog days of August. Still, when combined with his hot streak, the health and change-of-scenery aspects of O’Neill’s situation are at least worth keeping an eye on. He’s not going to continue slugging .906, but for a team whose outfielders entered this season ranking 22nd in the majors with a combined 96 wRC+ since 2020 — i.e., the post-Betts era — this counts as a welcome development.