Baseball's best players can make the game look easy at times, but maintaining high-level performance is hardly automatic. Even MVPs and Cy Young winners are vulnerable to the gravitational forces of the profession, namely injuries, aging, slumps and regression. Sometimes it can take more than a single season for luck -- good or bad -- or sheer randomness to even out, but when it does, those snazzy stat lines can take quite a hit.
As we look toward the 2019 season, here are five players -- all of them coming off solid to spectacular 2018 performances -- whose chances for drop-offs stand out for one reason or another. For some, key indicators from last year suggest their good fortune might run out. For others, our projection systems (at FanGraphs, we use a blend of Steamer and ZiPS for our depth charts projections) have a particularly pessimistic view, even if advancing age isn't a major factor. The players below are by no means the only ones expected to slip from 2018 to 2019, but they make for an interesting cross section of the ways in which decline can show itself. Of course, it's always worth remembering that projections are not destiny, and that the best players tend to be the ones who consistently beat the odds of falling off.
Scooter Gennett, Cincinnati Reds
There's no denying the Cincinnati second baseman's breakout has been a lot of fun. When a player who answers to "Scooter" succeeds, we all win. In 2017, Gennett became just the 17th player in major league history to homer four times in a game, and last year, his sixth in the majors, he made his first All-Star team while hitting .310/.357/.490 with 23 homers, a 125 wRC+ and 4.5 FanGraphs WAR (fWAR).
He's not especially old (29 on May 1), but two different methodologies suggest he's due for some significant regression. Via Statcast, Gennett had the largest gap between his wOBA (.362) and his xwOBA (.311) of any player with at least 500 plate appearances. What that means is that he was particularly lucky to be so productive given the combination of his average launch angle (13.2 degrees) and average exit velocity (86.7 mph), the latter of which ranked in just the 21st percentile.
Similarly, Gennett also has an MLB-high 51-point gap over the past two seasons (.364 wOBA, .313 xwOBA), 16 points larger than second-ranked Didi Gregorius, which suggests he's really pushing his luck. Meanwhile, our projections -- which are based on his past production, with no Statcast input at all -- forecast him for the majors' fourth-largest drop in fWAR (losing 2.6, falling to 1.9), with a 23-point dip in wRC+ (to 102). That's a long way down.
On the surface, Lester's 2018 season looks just fine. He went 18-6 with a 3.32 ERA, starting exactly 32 games for the fifth straight year (he has made at least 31 starts in 11 straight seasons) and making his fifth All-Star team. However, there are reasons for concern all over the place. He induced hitters to swing at a career-low 26.0 percent of pitches outside the strike zone (down from 32.5 percent in 2017), his swinging strike rate (8.5 percent) and strikeout rate (19.6 percent) were his lowest marks since 2013 (down from 10.9 percent and 23.6 percent in 2017, respectively), his ground ball rate (37.7 percent) was his lowest since 2008 (down from 46.2 percent in 2017), and his walk rate (8.4 percent) was his highest since 2011 (up from 7.9 percent in 2017).
All of that helps explain why his 4.39 FIP was his highest mark since his 63-inning 2007 campaign (up from 4.10 in 2017) and the minus-1.07 runs per nine gap between his ERA and FIP -- a quick-and-dirty indicator for regression -- was the majors' second highest. Meanwhile, the 21-point gap between his .319 wOBA allowed and his .340 xwOBA ranked eighth in the majors among qualifiers. By FanGraphs' FIP-driven WAR, the 35-year-old lefty is actually expected to rebound slightly thanks to slightly better strikeout and walk rates, from 1.7 in 2018 to 2.0 in 2019, but with an ERA jump to 4.17. Caveat emptor.
Blake Treinen, Oakland Athletics
Treinen's 2018 breakout anchored a beast of a bullpen, helping the upstart A's claim their first playoff spot since 2014. By both ERA (0.78) and FanGraphs WAR (3.6), he was the best reliever in baseball (though a case also can be made for Edwin Diaz based on his better strikeout and walk rates). The thing about relievers, though, is that it's very hard to maintain such dominance from year to year, and there are a fair number of things to be squeamish about with regard to this particular 30-year-old righty.
Start with the workload; with 80⅓ innings last year and 75⅔ the year before, Treinen ranks third in the majors in reliever innings, and he's just the 23rd reliever over the past decade to string together back-to-back 75-inning seasons. Only one reliever in that span has managed three straight years: the Mets' Jeurys Familia from 2014 to 2016, briefly Treinen's teammate last year. Meanwhile, the minus-1.04 runs per nine gap between his ERA and FIP (1.82) was Lester-like, and via Statcast, his 43-point gap between his .187 wOBA and .230 xwOBA was the majors' sixth largest among pitchers facing at least 250 batters. Our projections forecast him for a still-respectable 2.88 ERA, 2.96 FIP and 1.6 fWAR, but that's hardly dominant, and less than half the value the A's got from his stellar 2018.
Six years after he was drafted in the sixth round by the Indians -- who dealt him to the A's in December 2014, with Oakland in turn trading him to the Rays in December 2017 -- Wendle finally got the chance to put together an excellent rookie season last year, hitting .300/.354/.435 for a 116 wRC+ with 3.7 fWAR. The last mark tied Ronald Acuna Jr. and Juan Soto for the highest total among any MLB rookie last year.
That's the good news. More ominous is the way he got there. Wendle is a free swinger who hacked at 35.9 percent of pitches outside the zone (20th percentile) and walked just 6.8 percent of the time (24th percentile), so any drop in his .353 batting average on balls in play is going to take a huge bite out of his production. Such a drop seems likely, considering that he hits so many grounders; his .303 xwOBA, which was 35 points below his actual wOBA, ranked in the 29th percentile. Given his limited track record of success, he's projected for just an 86 wRC+ and 1.6 fWAR.
Boston's 26-year-old right fielder is coming off a storybook season in which he set across-the-board career highs in all three main rate stats -- .346/.438/.640, leading the AL in both batting average and slugging percentage -- and also wRC+ (185) and fWAR (10.4) -- en route to an MVP award as well as a championship ring. Alas, the most likely direction from any performance that stratospheric is down.
Consider this: In the post-1960 expansion era, position players have produced only 18 seasons of 10 fWAR or more. Five were achieved by Barry Bonds, three by Willie Mays (who also had one in 1954), two by Mike Trout, and one apiece by seven other players besides Betts. The 17 players who preceded Betts averaged 10.8 fWAR in their big year, and just 8.0 in their follow-up. Take the repeaters out of the equation and the average drop is from 10.5 WAR to 6.5.
All of which is to say that for Betts to maintain this level is quite unlikely, though to be fair, Trout is the only younger player to reach the 10 fWAR plateau, and it's conceivable that Betts, given his age, could continue to play at a similarly high level and could still be on an upward trajectory. Our projections suggest otherwise, forecasting him for an MLB-high 3.1 fWAR dip -- though his projected 7.3 fWAR in 2019 would still rank second, behind only Trout -- and a 43-point drop in wRC+. In most seasons that could still be an MVP-worthy season, just not quite as brilliant as what he did in 2018.