With Health on His Side, Zach Eflin Is Reaching New Heights

Tonight is a big night for Zach Eflin. When he takes the mound, he’ll be making his 19th start, and when he earns his second out of the evening, he’ll have retired his 318th batter, good for 106 innings on the year. Those aren’t records or nice round numbers, but they’re meaningful for this particular pitcher; he hasn’t surpassed those totals since 2019, his first and only qualified season. The Rays took a gamble on the righty this winter (by their own standards, at least), signing the oft-injured starter to the largest free-agent deal in franchise history. When Drew Rasmussen and Jeffrey Springs each went down with season-ending injuries, the stakes for Eflin grew higher. But with each subsequent start he makes, his contract looks less like a gamble and more like highway robbery. When Eflin records his second out tonight, he’ll have given the Rays more than he gave the Phillies in a single season since the pre-pandemic days.

Eflin nearly reached 106 innings his last time out, but the fates weren’t on his side. An hour-long rain delay messed with his preparation right before first pitch, and the hapless Royals chose that particular day to score five unanswered runs in the first two innings of play. Eflin was pulled shortly thereafter, and he would have to wait another five days to celebrate his achievement. Barring disaster, he’ll get there before 7:00 PM ET this evening, and all things considered, the timing actually works out quite well. His 106th inning will coincide with his 19th start, and his outing today will mark the latest date on the calendar that he’s started a game since 2020.

What makes tonight all the more special is the possibility of what’s to come. Eflin is on pace to make 30 starts and throw about 170 innings, both of which would be new career highs. When he qualified for the ERA title in 2019, he did so by the skin of his teeth, tossing 163.1 frames. He briefly lost his rotation spot after a disastrous performance that July (indeed, this season marks the first successful July of his career), and if the Phillies had optioned him to Triple-A instead of putting him in the bullpen, he’d have fallen 13 outs short of qualification. Thus, he’s looking to finish the season as a fully qualified starting pitcher for the very first time.

When Eflin was a youngster, FanGraphs prospect gurus praised his potential as a mid-rotation innings eater. So what went wrong? Injuries, as is often the case. Eflin’s 6-foot-6 frame has failed him at some point in every season of his big league career. He’s been on the injured list nine separate times since his debut in 2016 — ten if you count the COVID IL. The shortened 2020 season was the only year he avoided an IL stint, and even then, he dealt with back spasms during “summer camp,” pushing back his first start and limiting his pitch count in his first few outings. He dealt with back tightness earlier this year too – it’s become a chronic issue at this point – but this time around, he returned after the minimum 15 days and quickly got back on track. He’s looked sharp and healthy ever since.

Eflin has been the Rays’ most valuable pitcher this year, and his 2.6 WAR ranks eighth in the American League. A solid start tonight could bump him up to fifth place; a great start could get him all the way to third. Decimal points of WAR are about as meaningful as decimal points in your bank balance, but the further Eflin creeps up the leaderboards, the more attention he’s bound to get. And as he receives more recognition for his breakout performance, it’s worth remembering the pitcher he was before this season.

It would be easy to presume the Rays worked their magic to unlock something new from Eflin, but he has long been better than most people think. He took a huge step forward in 2020, but the shortened season brought his breakout to an early end. Injuries had the same effect in 2021 and ’22. On top of that, the dreadful Phillies defense always did him further disservice. His ERA was noticeably higher than every estimator in each year from 2020 to ’22. In other words, Eflin didn’t need any magic. He only needed to stay healthy for his $40 million deal to look like a bargain.

Here’s something that might surprise. Eflin has thrown 345.2 innings since the start of the 2020 season; 107 other pitchers have thrown at least 300 innings in that time. Among that group, Eflin ranks 21st in WAR per innings pitched, and he’s essentially in a seven-way tie with Luis Castillo, Framber Valdez, Logan Webb, Freddy Peralta, Alex Cobb, and Gerrit Cole. I’ll give you a moment to read those names again. It goes without saying that durability is an essential skill – there’s a reason WAR is a counting stat and not a rate stat – but the point is that Eflin never needed to make any dramatic changes to become a frontline starter. He just needed to stay on the field.

Indeed, as long as he’s healthy, pitching deep into games isn’t a problem for Eflin. He throws a ton of strikes but doesn’t rack up strikeouts, thereby keeping his pitch counts low. In addition, he has a couple of tricks up his sleeve that he can whip out when he needs a whiff to escape a jam. He ranks in the top third of pitchers in innings per start since 2020, and he rises into the top quarter if you remove some of his injury-affected outings.

Eflin struggled mightily in his final start of 2021 before hitting the injured list, and he slogged his way through three painful outings in 2022. Removing those four games from his ledger, he made 37 other starts over his last three seasons with the Phillies, posting a 3.87 ERA, 3.41 FIP, and 3.57 xFIP and averaging 5.77 innings per start. This year, in comparison, he has a 3.59 ERA, a 3.13 FIP, and 3.17 xFIP. Those numbers aren’t so different. Plus, it’s worth remembering that he moved to a pitcher-friendly home stadium and is pitching with a stronger infield defense behind him. All this to say, Eflin isn’t a brand-new pitcher. Things are just going his way for the first time in his career.

Now, this isn’t to say Eflin hasn’t improved; he certainly has! His ERA, FIP, xFIP, xERA, and SIERA are all career lows. He’s allowing more hard contact, but he’s also inducing more groundballs. His walk rate, which has always been excellent, is the lowest it’s ever been. On top of that, he’s earning swings and misses at the best rate of his career. That isn’t saying much for a guy whose whiff rate lives in the blue on Baseball Savant, but no pitcher is going to complain about extra swinging strikes.

Even better, Eflin is posting the best numbers of his career against left-handed hitters. He ditched his four-seam fastball against righties a few years back, and now he’s done the same against lefties. He’s spreading the love between his other pitches instead, and the results have been excellent. His curveball, in particular, has been nasty; opposite-handed hitters have a .169 wOBA and a 34.1% whiff rate against the curve, which they’re seeing over 30% of the time.

Ultimately, the key for Eflin has been focusing on what he already does well. He’s throwing his best pitches more often, and he’s focused on throwing strikes. Most importantly, he’s keeping the ball low in the zone. Take a look at the heat maps for his four most-used pitches, and you’ll see a total lack of color around the top of each image:

Eflin has excelled at keeping the ball low since he became a primary sinker-baller in 2020, but this year he’s reached another level. Out of 124 pitchers with at least 1,000 pitches this season, only two (Marcus Stroman and Carlos Carrasco) have thrown a lower percentage of their strikes in the upper third of the zone. Furthermore, neither Stroman nor Carrasco throws nearly as many strikes as Eflin. They both rank among the bottom 20% in zone rate, and Eflin ranks in the top 15%. Of the 51 starters who’ve thrown at least 50% of their pitches in the zone, none avoids the upper third like Eflin. In part, this reflects the fact that he’s throwing fewer four-seam fastballs, but it also demonstrates refined control of his cutter, which has become a key weapon in his arsenal.

Eflin’s primary reason for keeping the ball low is clear: He wants to induce groundballs and called strikes, both of which come more frequently on pitches further down in the zone. But there’s a secondary benefit, too. Opposing hitters are almost never expecting a pitch above their waist, and Eflin dominates when he surprises them up in the zone. He has held opponents to a .240 wOBA and .260 xwOBA on pitches in the upper half, and his strikeout rate in the upper third is almost double his strikeout rate over the rest of the plate.

All these improvements have helped Eflin put together the best performance of his career, but at the end of the day, none of it would make a difference if he couldn’t stay on the field. He isn’t breaking out because of a new pitch or a new approach. He’s breaking out because he’s finally healthy, and he’s finally pitching enough for the baseball world to take note.