By Rich Arleo

The 2017 MLB season has been dominated by offense, but that doesn’t mean there haven’t been great pitching performances. While the usual suspects like Clayton Kershaw, Max Scherzer, Chris Sale and Corey Kluber have all been unsurprisingly dominant, there have also been major breakouts from a number of young arms. A few of these young pitchers have not only taken it to another level this year, they’ve posted numbers that put them up there with the likes of Kershaw, Scherzer, et. al.

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Here are five surprises aces this season:

Luis Severino – New York Yankees

A quick glance at Severino’s stats this season show you an impressive young starter who has done a 180 after a difficult season and become the No. 1 starter many within the Yankees organization had hoped. When you take an even closer look, you’ll see a dominant ace who has put up a season comparable with the league’s best.

Severino, a top prospect with New York since he signed as an international free agent in ’11, debuted with the Yankees two seasons ago and showed flashes of brilliance over 11 starts, posting a 2.89 ERA in 62 1/3 innings. While many expected him to build on that the following year, his 3.72 xFIP, 4.37 FIP and lackluster 8 K/9 show that he may have outperformed his pitching in his rookie year. That’s exactly what happened, and Sevy took a major step back last season while struggling to a 5.83 ERA as some jumped to conclusions that he may just be destined to be a late-innings reliever. Still just 23 years old entering this season, Severino was determined to prove he can be a front-line starter, and he’s done that and then some.

The Yankees’ young right-hander got off to a quick start and never looked back, and as we enter September he has placed himself in the Cy Young Award discussion (though Sale and Kluber are the clear leaders). Among MLB starters, Severino ranks in the top 10 in K/9 (10.6), K% (28.6), ERA (3.14), WHIP (1.10), FIP (3.23), xFIP (3.05) and WAR (4.4). He’s also the only starter with a K/9 over 10 to have a groundball rate over 50 percent.

Unlike his rookie season, there aren’t many, if any, underlying concerns for regression and it’s clear that a healthy Severino can be the Yankees’ ace for a long time.

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Jimmy Nelson – Milwaukee Brewers

Glancing down the pitching WAR (wins above replacement) leaderboard, you see mostly usual suspects, except for one: Sale, Kluber, Scherzer, Chris Archer … Jimmy Nelson? Currently fifth in baseball with a 4.5 WAR, the little-known Nelson still isn’t getting much attention while keeping Milwaukee in the National League Central race.

A second-round pick by the Brewers in ’10, Nelson entered his fourth MLB season at 28 years old coming off a 16-loss campaign with a career 4.38 ERA. Nelson led the NL in three categories last season: losses, walks (86) and batters hit (17). This year, he leads the league in starts and is in the top 10 in HR/9 (0.88), WAR (4.5), FIP (3.10) and xFIP (3.17). He also has the second-highest K/9 (9.97) among pitchers with a ground-ball rate over 50%.

Nelson has seen dramatic improvement in the swings and misses he’s generating, with his SwStr% (swinging strike percentage) rising from 7.4 last season to a career-high 11.4 this year. He’s also getting more swings out of the zone and has seen hitters’ contact rates drop a full eight points down to 77% this year, another career best. Nelson credits a change in the lower half of his delivery to his newfound success. While the change hasn’t resulted in a large uptick in velocity, it has drastically helped with his control, which has helped Nelson gain confidence in all of his pitches, especially his curveball. A pitch he developed and found success with in ’15, he largely abandoned it last year, throwing it only 11% of the time. This year he’s using the curveball 19% of the time and it’s garnered a 9.6 rating, according to Fangraphs.

If Nelson can maintain the control he’s found this season, he’ll continue to get swings and misses at a high rate and finish the season strong for Milwaukee as one of the best starters in baseball.

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Alex Wood – Los Angeles Dodgers

The Dodgers have had an embarrassment of riches the year, arguably none better than the development — and relative health — of Wood. A former second-round pick of the Braves, Wood pitched parts of three seasons in Atlanta before being traded to Los Angeles in a three-team deal in which the Dodgers gave up a handful of prospects, none of whom have panned out.

Wood showed some promise in Atlanta and had a decent ’16 season for the Dodgers before he succumbed to injury. While Wood has spent some time on the DL this year, he’s stayed relatively healthy and looks to continue his breakout season down the stretch.

Wood is a few innings shy of qualifying among season leaders, but barring another injury after his return to begin September he should be qualified by the end of the season. Beyond Wood’s sparkling 14-1 record, he is in the top 10 among starters in ERA (2.41), FIP (2.95), xFIP (3.05), GB% (56.3), BAA (.206) and WHIP (1.01). Wood is keeping hitters off balance this season, forcing a 35.9 O-Swing% (third best in baseball) and getting a ton of swings and misses. His 12.4 SwStr% is easily a career best and is almost three percentage points higher than his career average. Wood uses his sinking fastball almost 50% of the time, and it’s rated as the seventh most valuable sinker according to Fangraphs’ Pitch Type Values. His changeup has been even better, and its 13.9 rating is third best.

With Kershaw and Wood returning to the rotation as the calendar turns to September, the Dodgers are locked and loaded with two aces (arguably four aces with Yu Darvish and Rich Hill) at the top of their rotation entering the postseason.

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Aaron Nola – Philadelphia Phillies

Nola having a strong ’17 season can’t be classified as a complete surprise, but after a disappointing ’16, Nola has taken steps forward to become one of the better starters in the NL this year. The Phillies’ No. 7 overall selection in the ’14 draft, Nola was fast-tracked through the Minors, debuted in ’15 and was a full-time member of the rotation last year. Nola looked to have it all figured out quickly after a dominant start last season, posting a 2.65 ERA and .212 BAA with 85 strikeouts in 78 innings over his first 12 starts. He then posted a 9.82 ERA in his next eight starts before his season ended with an elbow injury. Nola fortunately didn’t need Tommy John Surgery and has come back in a big way this year.

Nola’s 3.46 ERA, 3.6 WAR, 49 GB% and 9.2 K/9 through 22 starts all rank in the top 20 in baseball, and his 0.85 HR/9 and 3.22 FIP are top 10. Nola’s upped his SwStr% from 9.6 to to 10.4 this year and his fastball — which garned a -8.4 Pitch Value last year — is now rated 5.0 with the velocity up a full MPH to 92.4.

Last season, despite the 4.78 ERA, Nola’s .334 BABIP and 3.08 FIP showed there was some bad luck in play, and he has proved that this season and looks like the ace of the future for the Phillies.

James Paxton – Seattle Mariners

Since Paxton debuted with the Mariners in ’14, fans have been waiting for a full season out of him to see just what he can do. Injuries unfortunately have been the big story in his young career. The young left-hander from Canada, ‘Big Maple’ as many call him, missed much of ’15 with a finger issue and then had two separate stints on the DL last season. When healthy, Paxton has pitched well, and while injuries have again struck this season, he’s been one of the most dominant pitchers in baseball when on the mound this year.

Paxton has gone 12-3 over 20 starts for the Mariners, who are missing both he and Felix Hernandez as they push for a Wild Card spot. Should he have enough innings to qualify, he’d rank seventh in MLB with a 2.78 ERA and 3.15 xFIP, and second only to Sale with a 2.50 FIP. He’s also top 10 with a 10.38 K/9 and leads baseball having given up just seven homers in 119.2 IP (0.53 HR/9).

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The lefty dominates with a 96-MPH fastball with a pitch value of 19.6 (behind just Sale and Justin Verlander) which is mixed in with a cutter to go along with a changeup and a knuckle curve. Paxton’s 12.7 SwStr% is one of the highest in the league and batters have managed to hit just .215 against him. Currently dealing with a pectoral injury, the Mariners hope to have him back in mid-September. If they can get Paxton and King Felix back for the final few weeks of the year, they’ll have a good shot at snagging a Wild Card spot.