The ERA leaderboards tell you a lot about which pitchers had great seasons. This year, Jacob deGrom and Blake Snell won their league ERA titles, then both won their league's respective Cy Young Award, and they were well-deserving. But for some pitchers, there's more to the story.
Statcast™ can help identify those pitchers. By tracking the exit velocity and launch angle of every batted ball, and combining that information with strikeout and walk totals, Statcast™ gives each pitcher an "expected wOBA" (xwOBA) -- a metric, scaled like on-base percentage, that's meant to show how well a pitcher has really performed based on the quality of contact he's allowed.
If a pitcher's expected wOBA was a lot lower than his actual wOBA allowed, chances are he was pitching better than he had to show for it in his results. And if he keeps suppressing quality of contact at the same level, he might be due for a stat-sheet correction.
Here are nine starting pitchers to watch entering 2019, who had a large "unlucky" gap between their contact quality allowed and their actual results this season.
1. Thomas Stripling, Dodgers: 52-point gap
2018 expected wOBA: .264 | Actual wOBA: .316
Stripling was a breakout All-Star for the Dodgers in 2018 after moving into the rotation at the end of April, but toe and back issues and pitch-tipping concerns derailed his second half, and he ended up left off Los Angeles' postseason rosters. Overall as a starter, he finished the year with a 3.39 ERA and 119 strikeouts in 106 1/3 innings. There's a lot of good to focus on heading into next season. Of 134 starting pitchers to face at least 400 batters in 2018, Stripling's .264 xwOBA was tied for eighth-lowest. It was more than 50 points better than the MLB average for starting pitchers (.315). Stripling's actual wOBA as a starter, by comparison, ranked 73rd. The 52-point gap between his xwOBA and actual wOBA was the largest among those 134 starters.
Lowest xwOBA allowed, NL starting pitchers, 2018
Minimum 400 batters faced

1. Jacob deGrom: .242
   2 (tie). Max Scherzer: .247
   2 (tie). Walker Buehler: .247
   
2. Aaron Nola: .257
   5 (tie). Ross Stripling: .264
   5 (tie). Noah Syndergaard: .264

The one caveat is the Dodgers will have to hope that Stripling is fully healthy and has corrected his mechanical issues. The 29-year-old right-hander's second-half struggles were real -- even his xwOBA ballooned to .347 in his seven starts after the All-Star break. In twice as many starts before the break, though, his xwOBA was a sparkling .234, third-best among all starters behind only Justin Verlander and Chris Sale.
2. Dylan Bundy, Orioles: 41-point gap
xwOBA: .322 | wOBA: .363
Bundy made 31 starts at the front of an Orioles rotation that went through some severe struggles in 2018, and he finished the season with a 5.45 ERA over 171 2/3 innings. But the quality of contact numbers suggest things shouldn't have been so extreme for the 26-year-old right-hander. Bundy's 41-point gap between his xwOBA and actual wOBA allowed was the second-largest among starters behind only Stripling's.
Bundy's slider is a good place to look for optimism. It was an excellent swing-and-miss pitch this season -- opponents whiffed on 50.0 percent of their swings against his slider, and Bundy racked up 118 strikeouts on sliders, fourth-most of any pitcher. But the numbers on his slider maybe should have been even better. Bundy allowed a .178 batting average in at-bats ending on sliders, though his expected batting average allowed on sliders was just .119. He allowed a .370 slugging percentage on sliders, but his expected slugging percentage was just .195. Bundy also has a high-spin four-seam fastball that can play well up in the zone -- he averaged 2,416 rpm, a top 10 mark among starters who threw at least 500 four-seamers and well above the 2,263 rpm MLB average.
Highest whiff rate on sliders, starting pitchers, 2018
Minimum 100 sliders swung at

1. Patrick Corbin: 53.6 percent
   
2. Kyle Gibson: 51.0 percent
   3. Dylan Bundy: 50.0 percent
   
3. Carlos Carrasco: 48.6 percent
   
4. Felix Pena: 48.5 percent

3, 4 and 5. Nick Pivetta / Vince Velasquez / Zach Eflin, Phillies
Pivetta: 35-point gap (xwOBA: .288 | wOBA: .323)
Velasquez: 30-point gap (xwOBA: .295 | wOBA: .325)
Eflin: 27-point gap (xwOBA: .292 | wOBA: .319)
Three of the Phillies' five starters ranked among the top 10 largest "unlucky" gaps between xwOBA and wOBA in 2018: Pivetta (third), Velasquez (fifth) and Eflin (tied for 10th). A big culprit was likely the Phillies' defense. By Defensive Runs Saved, Philadelphia was the worst fielding team in baseball by a wide margin: their -146 DRS was 46 runs fewer than the next-worst team, the Blue Jays. That's reflected in the gap between this group of starters' ERAs and Fielding Independent Pitching: Pivetta had a 4.77 ERA with a 3.79 FIP, Velasquez a 4.85 ERA with a 3.75 FIP and Eflin a 4.36 ERA with a 3.80 FIP.
If the Phillies can make some upgrades defensively this offseason or their fielders work to improve entering 2019, their starting pitchers could see a boost in their numbers in turn. It also helps that the Philadelphia rotation has some good strikeout stuff. The 25-year-old Pivetta struck out 188 batters in 164 innings this season, featuring one of the higher-spin curveballs among starting pitchers (he averaged 2,840 rpm, with MLB average being 2,492 rpm). The 26-year-old Velasquez struck out 161 in 146 2/3 innings, including 109 on his four-seam fastball, tied with Jacob deGrom for sixth-most of any pitcher. And the 24-year-old Eflin struck out 123 in 128 innings.

6. Carsten Sabathia, Yankees: 25-point gap
xwOBA: .288 | wOBA: .313
The 38-year-old veteran has been a valuable depth starter for the Yankees' playoff teams of the last two seasons, and New York agreed to a one-year deal to bring Sabathia back for one more year in 2019, likely his final Major League season. There's good reason to believe that Sabathia can continue to pitch effectively -- he's been excellent at limiting hard contact.
Sabathia held hitters to an average exit velocity of just 84.4 mph this season, second-lowest of 128 starting pitchers who allowed 300-plus batted balls. He also had one of the lowest hard-hit rates allowed. Statcast™ defines a hard-hit ball as having an exit velocity of 95 mph or higher; barely one in four batted balls against Sabathia met that threshold. Sabathia has been consistent in limiting hard contact over the last several seasons, and that bodes well for 2019.
Lowest hard-hit rate allowed, starting pitchers, 2018
Minimum 300 batted balls allowed

1. Anibal Sanchez: 26.3 percent
   
2. Noah Syndergaard: 26.4 percent
   3. CC Sabathia: 26.6 percent
   
3. Chris Sale: 26.8 percent
   
4. Zack Wheeler: 27.1 percent

7. Noah Syndergaard, Mets: 22-point gap
xwOBA: .264 | wOBA: .286
Syndergaard had a 3.03 ERA and 155 strikeouts in 154 1/3 innings in 2018. That's good. But when you consider how dominant his stuff is, you wonder if those numbers shouldn't be even better. That's where his expected wOBA comes in: it was tied for eighth-lowest among starters, and more than 20 points lower than his actual wOBA allowed. He's extremely difficult to square up. Syndergaard allowed hard contact on just 26.4 percent of batted balls, the second-lowest hard-hit rate among starters. He allowed barrels -- the most dangerous combinations of exit velocity and launch angle -- on just 2.0 percent of batted balls, the lowest rate among starters.
Lowest barrel rate allowed, starting pitchers, 2018
Minimum 300 total batted balls allowed
1. Noah Syndergaard: 2.0 percent
2 (tie). Walker Buehler: 3.8 percent
2 (tie). Mike Montgomery: 3.8 percent
4. Jacob deGrom: 4.1 percent
5 (tie). Dereck Rodriguez: 4.2 percent
5 (tie). Sean Newcomb: 4.2 percent
Thor can overpower hitters with any pitch in his arsenal. His average fastball velocity (combined four-seamer, two-seamer and sinker) was 97.4 mph in 2018, second-highest among regular starters behind Luis Severino. His average slider velocity was 92.0 mph, highest among regular starters. His average changeup velocity was 90.3 mph, highest among regular starters. And even his average curveball velocity was 83.1 mph, third-highest among regular starters.

8. Lance Lynn, free agent: 21-point gap
xwOBA: .309 | wOBA: .330
Lynn's overall numbers for 2018 didn't look great -- in his 29 starts, he had a 4.94 ERA -- but he showed flashes with the Yankees down the stretch, and his strikeout ability is encouraging (he had 152 strikeouts in 149 1/3 innings as a starter). Most of the pitches Lynn throws are fastballs of some variety (88.6 percent, the heaviest fastball usage among starters), but he keeps the ball out of the heart of the strike zone (just 5.7 percent of the pitches he threw were middle-middle) and doesn't allow many barrels (just 4.3 percent of his batted balls, tied for seventh-lowest among regular starters). The 31-year-old could be an interesting free agent.

9. Matt Harvey, free agent: 21-point gap
xwOBA: .308 | wOBA: .329
Harvey's interesting, too, especially considering all the highs and lows he's gone through. The 29-year-old showed a lot of improvement with the Reds after his trade from the Mets, and his stuff got sharper as the season went on. Harvey's average four-seam fastball velocity climbed from 92.5 mph in April to 93.8 mph in May to 94.3 mph in June to 94.7 mph in July, and though it dipped a little to 94.1 mph in August, it rose back to 94.7 mph in September. In Cincinnati, he started to regain some of his old velocity for the first time in a long time. In a June start against the Cubs, he hit 97 mph for the first time in over a year. In his last start of July against the Phillies, he dialed it up to 97-plus for multiple strikeouts, the first time he had done so since his memorable Game 5 start for the Mets in the 2015 World Series against the Royals.