The concept of an ace comes up a lot in baseball conversations, usually without a specific definition. In scouting, it comes up just as often and has a bit more of a specific meaning, but it can vary from person to person. The basic idea, in a scouting sense, is that an ace is part of the top tier of starting pitchers and that this tier is more than five or six pitchers but less than 15 -- with most scouts and executives putting it at eight to 12.
I've never heard it described this way, but it makes sense to think of it as basically one ace per playoff team, excepting last year's 16-team free-for-all. It worked out that the playoff format currently includes 10 teams and the list right now has 10 pitchers -- but it won't always be that way.
This ranking, which we will regularly update to keep track of what the top of the big leagues looks like to evaluators, is projecting a bit. But since it's for right now and the rest of this season, it's basically evaluating what a guy can do at the moment -- not whether he'll make the leap in the years ahead. There's a big example that I'll get into below of an injured ace, and he won't qualify for this set of the rankings, but I'll keep his seat warm. As with almost all of my rankings, this is my opinion but has a lot of industry views folded into it.
1. Jacob deGrom, New York Mets, 32 years old (Tommy John surgery in 2010)
2018-20 IP: 217.0, 204.0, 68.0 (3-year total: 489.0, 1st)
2018-20 ERA: 1.70, 2.43, 2.38 (3-year average: 2.10, 1st)
2018-20 xFIP: 2.60, 3.11, 2.46 (3-year average: 2.80, 2nd)
2018-20 WAR: 9.0, 7.0, 2.6 (3-year total: 18.7, 1st)
DeGrom almost won all four of the categories I'm tracking here and was the consensus winner from the evaluators I surveyed. There isn't much more to say, but I will point out that a big part of the reason that deGrom has continued to improve over the years is his increasing velocity (2016-21: 93.4, 95.2, 96.0, 96.9, 98.6, 99.2), especially surprising given his age and decade-plus with a new elbow ligament. Outliers keep outlying?
2. Gerrit Cole, New York Yankees, 30 years old
2018-20 IP: 200.1, 212.1, 73.0 (3-year total: 485.2, 3rd)
2018-20 ERA: 2.88, 2.50, 2.84 (3-year average: 2.71, 4th)
2018-20 xFIP: 3.04, 2.48, 3.38 (3-year average: 2.84, 3rd)
2018-20 WAR: 5.9, 7.3, 1.5 (3-year total: 14.7, 3rd)
Cole was a consensus second for this list, and the figures above along with his monster $324 million contract and the eye test all back that up. His velocity over his last three seasons and his 2021 debut are all within a 0.6 mph spread, which along with his age bodes well going forward. His best season was his contract year in 2019 with Houston, but his 13 regular-season and three postseason starts for the Bombers have essentially met expectations.
3. Shane Bieber, Cleveland Indians, 25 years old
2018-20 IP: 114.2, 214.1, 77.1 (3-year total: 399.2, 23rd)
2018-20 ERA: 4.55, 3.28, 1.63 (3-year average: 3.22, 16th)
2018-20 xFIP: 3.30, 3.23, 2.04 (3-year average: 3.00, 4th)
2018-20 WAR: 2.6, 5.2, 3.2 (3-year total: 11.6, 6th)
Bieber was a consensus third choice and the last (healthy) pitcher clearly in the top tier. He's also the youngest on this list and is coming off a Cy Young win in 2020. He's the example of the more progressive approach to pitching development Cleveland is on the bleeding edge of right now. The philosophy is for teams to focus on acquiring pitchers with strong command and athleticism, then have them develop more velocity and off-speed quality largely by using data. In line with this, Bieber uses his changeup less than 10% of the time, which is becoming a more popular approach.
4. Walker Buehler, Los Angeles Dodgers, 26 years old (TJ in 2015)
2018-20 IP: 137.1, 182.1, 36.2 (3-year total: 355.1, 43rd)
2018-20 ERA: 2.62, 3.26, 3.44 (3-year average: 2.91, 9th)
2018-20 xFIP: 3.21, 3.37, 3.93 (3-year average: 3.34, 14th)
2018-20 WAR: 3.1, 5.0, 0.5 (3-year total: 8.8, 18th)
Buehler has pitched like a mid-to-lower-3.00-ERA pitcher since his big league debut in 2017, with his average velocity holding around 96-97 mph. His 3.40 xFIP in the regular season (371.2 IP) is topped by his 2.88 xFIP in the postseason (61.1 IP), which helped Buehler move to the top of this next tier of starters. You could rank him, Trevor Bauer and Clayton Kershaw in almost any order, but I'll take the combination of velocity, youth and track record.
5. Aaron Nola, Philadelphia Phillies, 27 years old
2018-20 IP: 212.1, 202.1, 71.1 (3-year total: 486.0, 2nd)
2018-20 ERA: 2.37, 3.87, 3.28 (3-year average: 3.13, 11th)
2018-20 xFIP: 3.21, 3.82, 2.79 (3-year average: 3.41, 18th)
2018-20 WAR: 5.5, 3.5, 2.0 (3-year total: 11.0, 8th)
Compared to most of the pitchers below, Nola has been positively boring; no arm surgery, no terrible season, no controversies, no nine-figure free-agent deal -- just consistently elite performance. We haven't seen Nola pitch in the postseason, and he may never be in the top couple of spots on this list, but he's one of the most valuable pitchers in the league.
6. Trevor Bauer, Los Angeles Dodgers, 30 years old
2018-20 IP: 175.1, 213.0, 73.0 (3-year total: 457.1, 7th)
2018-20 ERA: 2.21, 4.48, 1.73 (3-year average: 3.21, 14th)
2018-20 xFIP: 3.14, 4.33, 3.25 (3-year average: 3.71, 31st)
2018-20 WAR: 5.8, 3.3, 2.5 (3-year total: 11.5, 7th)
Bauer has had some inconsistency in his last five seasons, with a mediocre career relative to his draft pedigree until a step forward in 2017, then a breakout 2018 season for Cleveland, followed by a decent 2019 when he was traded to Cincinnati, then a Cy Young 2020 with the Reds that led to a free-agent payday with the Dodgers. He has been strong in the postseason and has his original UCL, with a constantly evolving pitch mix. The fallout from recent reports around Major League Baseball's renewed effort to curtail the illegal use of foreign substances on baseballs could affect his (and others') stock for this list in future iterations.
7. Yu Darvish, San Diego Padres, 34 years old (TJ in 2015)
2018-20 IP: 40.0, 178.2, 76.0 (3-year total: 294.2, 74th)
2018-20 ERA: 4.95, 3.96, 2.01 (3-year average: 3.60, 34th)
2018-20 xFIP: 4.24, 3.39, 2.82 (3-year average: 3.36, 16th)
2018-20 WAR: 0.2, 2.5, 3.0 (3-year total: 5.7, 44th)
Darvish has years of elite performance and steady velocity that is trending up of late but also a profile complicated a bit by elbow surgery. Darvish has had the best velocity of his career in 2020 and 2021, and is coming off a second-place finish in the 2020 NL Cy Young voting before moving to the most exciting team in baseball. He's 34, and there aren't really any signs of decline right now, but the risk is in his age and homer-prone stretches.
8. Stephen Strasburg, Washington Nationals, 32 years old (TJ in 2010)
2018-20 IP: 130.0, 209.0, 5.0 (3-year total: 344.0, 49th)
2018-20 ERA: 3.74, 3.32, 10.80 (3-year average: 3.51, 32nd)
2018-20 xFIP: 3.28, 3.17, 5.69 (3-year average: 3.25, 11th)
2018-20 WAR: 2.4, 5.6, 0.0 (3-year total: 8.1, 24th)
If healthy, I'd very slightly rather have Strasburg over Max Scherzer, but that's the rub. Strasburg isn't always healthy: He missed almost the entire 2020 season with surgery for carpal tunnel, then had a nagging calf injury this spring before looking solid in his first regular-season start. If Strasburg's playoff run in 2019 wasn't so incredible (36.1 innings, 1.98 ERA, 2.38 xFIP) then I'd just take the certainty of Scherzer, but the upside is too much to pass on.
9. Max Scherzer, Washington Nationals, 36 years old
2018-20 IP: 220.2, 172.1, 67.1 (3-year total: 460.1, 6th)
2018-20 ERA: 2.53, 2.92, 3.74 (3-year average: 2.85, 7th)
2018-20 xFIP: 3.06, 2.88, 3.53 (3-year average: 3.06, 5th)
2018-20 WAR: 7.5, 6.5, 1.8 (3-year total: 15.8, 2nd)
You can see from Scherzer's stats over the last three years that he is right there with the best pitchers in baseball in every category, and he passes the eye test with playoff performance to boot. He's 36, so you have to believe his decline phase is near, but you have to pitch your way off this list, and he simply hasn't. A large part of it is that he's held the same velocity for six seasons (94.1 to 94.9 mph), with 2019 and 2020 the highest of the run.
10. Lucas Giolito, Chicago White Sox, 26 years old (TJ in 2012)
2018-20 IP: 173.1, 176.2, 72.1 (3-year total: 422.1, 17th)
2018-20 ERA: 6.13, 3.41, 3.48 (3-year average: 4.54, 92nd)
2018-20 xFIP: 5.46, 3.66, 3.35 (3-year average: 4.35, 72nd)
2018-20 WAR: 0.1, 5.1, 2.0 (3-year total: 7.1, 31st)
I almost didn't include Giolito, as his track record of being good has consisted of only 42 starts (counting his first 2021 start) and he was hovering around replacement value until that time. He got the benefit of the doubt for reasons that together help move the needle: His start to 2021 has been strong, his pitch mix and arm action are recent improvements/evolution and the ZiPS projection system has him as the third-best pitcher in baseball with the best projected ERA among all starters. That said, if you want more bulk performance than this to declare Giolito an ace, you could make the case for sliding him off the back and letting this sit at nine pitchers to start the year.
Injured ace in waiting
Chris Sale, Boston Red Sox, 32 years old (TJ in 2020)
2018-20 IP: 158.0, 147.1, 0.0 (3-year total: 305.1, 68th)
2018-20 ERA: 2.11, 4.40, missed season (3-year average: 3.21, 15th)
2018-20 xFIP: 2.31, 2.93, missed season (3-year average: 2.61, 1st)
2018-20 WAR: 6.2, 3.6, 0.0 (3-year total: 9.8, 12th)
Sale broke up deGrom's chance to top all four categories by leading in xFIP, but doing it in one less season since he missed the shortened 2020 because of Tommy John surgery. Sale is among six who have had that surgery among the 11 aces mentioned here, which is more than I was expecting and probably a good fact to keep in mind come draft or prospect ranking time. It's still definitely not a good thing and the just-missed list doesn't have many TJs on it, so I think the takeaway is that an elbow surgery won't necessarily greatly harm the ability of a Cy Young-level pitcher. If he hadn't been hurt, or if he returns later this season right where he left off, Sale breaks somewhere into that top tier of three.
Others in the mix
RHP: Luis Castillo, Tyler Glasnow, Corbin Burnes, Brandon Woodruff, Zack Wheeler, Charlie Morton, Jack Flaherty, Lance Lynn, Joe Musgrove, German Marquez, Sonny Gray, Jose Berrios
LHP: Clayton Kershaw, Hyun Jin Ryu, Max Fried, Blake Snell, Patrick Corbin, Jesus Luzardo
Injured: Justin Verlander, Mike Clevinger, Dinelson Lamet, Noah Syndergaard
Prospects on the horizon: Ian Anderson, Sixto Sanchez, Nate Pearson, MacKenzie Gore, Casey Mize, Michael Kopech, Matt Manning, Luis Patino, Grayson Rodriguez, Max Meyer, Quinn Priester
These players are in a general order within each category, so a hot month or two could get the younger crop of the just misses -- Castillo (the last cut), Glasnow or the two Brewers starters -- onto the list in the next update, while the veterans will have a slightly harder time breaking through given their longer track records and unlikely (but possible) sudden improvement.