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Aces Wild: The case for Luis Severino and James Paxton as top starters

We may not know for how many innings they will shine, but the Yankees’ rotation features a pair of undeniable stars.

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Are Luis Severino and James Paxton aces? That depends on one’s definition of the word. Based on pure talent level, the pair certainly qualifies. Yet, for those who reserve the title of “ace” for only the consistently excellent, year in and year out, perhaps the two pitchers aren’t quite at that level. Both do come with their fair share of questions. Brian Cashman and the Yankees’ brass has entrusted the top of the rotation to these two talented hurlers. Should we be at ease, or should we worry?

First, we must note that Severino and Paxton’s talent level is sky-high. To do so, consider their ranks in terms of K-BB% among starters the past two years, thanks to FanGraphs Leaderboards.

Why K-BB%? As far as gauging the skill level of a given pitcher goes, there’s no stat that captures so much with so little. Unlike other stats in the sabermetric vernacular, the math behind K-BB% is easy to understand; just subtract walk rate from strikeout rate, and voila. The stat’s simplicity stems from the clarity of the concept behind it. What does the ideal pitcher do? Not give up runs. What’s the simplest way to do that? Punch out as many batters as possible while keeping free passes to a minimum. The wider the difference between a hurler’s strikeout and walk rates, the better.

Which pitchers have run the best K-BB% marks in MLB over the past two years? Here’s a look at the top 10:

Let’s walk through the list from the beginning. Atop the list is Chris Sale, who has a pretty solid case for the title of “best pitcher in the game as of now”. Behind him is Max Scherzer, who owns an equally convincing claim to said moniker. Corey Kluber and Jacob deGrom, also plausible contenders for “best-in-MLB” status, occupy spots three and four. At fifth place, we find none other than Paxton.

By K-BB%, a stat in which the essence of the ideal pitcher is distilled, only four pitchers in all of Major League Baseball have bested Paxton over the last two years. All of them are among the best pitchers in the game. In terms of pure ability, it’s high-time we included Paxton in that group.

Let’s continue down the list. At sixth place, narrowly behind Paxton, we find Justin Verlander, whose late-career renaissance has propelled him back to elite status. Seventh place belongs to Carlos Carrasco - perhaps not quite on the same level in terms of reputation as some of the aforementioned arms, but an elite pitcher nonetheless. Then at eighth place, Severino appears on the list, with 450 strikeouts compared to just 97 free passes over the past two seasons. If you aren’t impressed by that, note that he’s ranked above ninth-place Clayton Kershaw and tenth-place Stephen Strasburg. I’m not aware of many fans that question their talents.

Again, this is basically a list of the 10 best pitchers in MLB, and two of them call the Yankees’ rotation home. Only two other teams have duos who are both included in the list - Washington, with their Scherzer/Strasburg combo, and Cleveland, with their Kluber/Carrasco one-two punch. Severino/Paxton might not have the same ring to it as the other two, but rest assured, in terms of their core skills - getting tons of strikeouts while limiting walks - they are just as deadly.

Of course, there’s a catch - there’s always a catch. For Paxton, the question has never been his performance; rather, it’s been his health. Full disclosure: when creating the leaderboard above, I set the minimum for innings pitched over the past two seasons at 250. Otherwise, Paxton, whose 2017-18 innings total amounts to just 296.1 frames, would not have appeared on the list. This is despite the fact that the fire-balling lefty established career highs in innings pitched in both 2017 and 2018. If you define an ace as a pitcher who provides both quality and quantity, you’d find Paxton lacking in the latter criteria.

Dig deeper on Paxton’s injuries, however, and we can find cause for optimism regarding his health going forward. We’d have every reason for anxiety if Paxton’s injuries were of a recurring type, or if they had involved his throwing shoulder or elbow ligaments. A quick look at Paxton’s injury history reveals that this isn’t the case. Here’s the full list of the injuries that the Big Maple has suffered since his MLB debut, along with the amount of time he missed due to each issue (courtesy of a Brendan Kuty piece on

2014: lat strain (four months)

2015: left finger tendon strain (four months)

2016: line drive to the elbow (two weeks)

2017: forearm strain, pectoral strain (two months)

2018: back inflammation, line drive to the left forearm (five weeks)

True, that’s a hefty number of injuries and missed time over the span of five seasons. Yet the record also shows that Paxton’s left shoulder and elbow ligaments have been issue-free so far. His injury history can be summarized as the following - a series of strains, all in different places; bad luck with line drives; and an aching back.

Strains are painful, but aside from very serious instances they do not require surgery, and once healed, the injured muscles regain their functionality. As for luck with line drives, that can be chalked up to misfortune (though if I were Paxton I’d see a shaman just in case). Finally, back pain is no joke, but it’s also in no way a death knell for an athlete save for severe, chronic cases.

All in all, Paxton’s injury record suggests that his time on the injured list has been a combination of tedious but non-career-threatening injuries and bad luck. The odds of him setting a new career high in innings pitched this year are better than you’d think if you just glanced at the back of his baseball card. Paxton may not sniff 200 innings, but 150-170 seems well within the realm of possibility. As long as he pitches to his talent level, that’s not a bad deal at all.

MLB: Spring Training-Toronto Blue Jays at New York Yankees Kim Klement-USA TODAY Sports

It’s surprising - and disappointing - to type this, but between the Yankees’ top two starters, Severino may be the bigger question mark. His shoulder ailment is a major concern, which came to light when he experienced discomfort while warming up for a scheduled start earlier this month. Fortunately, subsequent MRIs revealed the injury to be rotator cuff inflammation, rather than any serious structural damage to his shoulder. Even so, Severino was still shut down for weeks, and it now appears that he won’t return in April.

The best-case scenario is that rest and cortisone shots will allow the pain in Sevy’s shoulder to recede, enabling him to resume his throwing program and return at close to peak form while only missing about a month of the season. But there is always the risk of the injury flaring up again, especially if he rushes back from his recovery process. At this point, there’s no telling how much time Severino’s rotator cuff inflammation will force him to miss.

In addition to questions about his workload, the right-hander also faces questions about the quality of the innings he will provide. After looking like the front-runner for the AL Cy Young award in the first half of last season, Severino collapsed to the tune of a 5.57 ERA in the second half. The culprit was an inconsistent slider; Severino lost three inches of drop and two inches of break on the pitch after the All-Star break last year.

Without an effective slider, Severino only has two pitches - a fastball that is blazing fast but straight, and a still-developing changeup. That’s just not enough to navigate a major-league lineup with ease, especially if you’re giving hints as to what pitch is coming. Severino absolutely needs his slider in order to succeed, but no one knows whether it will be there for him all season long.

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That being said, the picture for Severino talent-wise is still extremely rosy. After his late July-early August nadir, Severino’s numbers recovered somewhat, as he posted a 4.11 ERA over his last seven starts of the regular season. And despite his ghastly second-half ERA, his FIP remained at a strong 3.37, suggesting that he was still getting strikeouts and limiting walks and homers at an elite pace. Most importantly, no matter how bad his second half was, that doesn’t erase the fact that his 2.31-ERA, 2.75-FIP first half happened too. For Severino, just like Paxton, the talent is clearly there. It’s just a matter of finding consistency and staying on the mound.

As we’ve seen above, Luis Severino and James Paxton are two of the best starting pitchers in the American League - provided they are healthy and right. Those “if”s are larger than you’d think, and larger than for most pitchers bestowed with the “ace” title, especially for a team with precious little rotation depth as currently constructed. At the same time, almost every other MLB team would kill for such clear and abundant talent in the top two slots of the rotation. Sure, Severino and Paxton are wildcards - you’re not quite sure what to expect from them. But no one’s going to blame you for betting on the two; after all, no one can deny the potential reward. Will they be aces this year, or will they be duds? We’ll find out soon enough.