Believability ratings for this season's most surprising starting pitchers

Let’s take a quick look at starting pitchers whose performance to date is very different from our preseason expectations.

We’ll give each pitcher a “believability rating” to reflect the likelihood that his performance is real. Keep in mind, these samples are still small.

The Outperformers

Ervin Santana of the Minnesota Twins has been one of the top-earning pitchers in the American League. Underneath, he isn’t doing anything that much different from 2016, when he had a 3.38 ERA — or 2015, when he had a 4.00 ERA.

The reason for his current 2.05 ERA? His .146 batting average on balls in play (BABIP). This is a ridiculously low number that will correct itself soon, and his ERA should rise.

Believability: Very Low

Jason Vargas of the Kansas City Royals has sparkled with a 2.03 ERA and a 1.03 WHIP. His skills, particularly his 4.3 strikeout-to-walk ratio (K/BB), look much improved, as they did in September when he returned from Tommy John elbow surgery.

Maybe his elbow has been hurting forever, because he had never shown these skills. Vargas is a better pitcher than he was, but not this much better.

Believability: Moderate

Dallas Keuchel won the Cy Young Award with the Houston Astros in 2015, so it’s his lousy 2016 that’s the surprise. He was hurt through much of last year, so his return to dominance is not a shocker. (His current non-arm injury is of little concern for the rest of the season.)

No American League pitcher has finished with a sub-2.00 ERA since 2000, and it’s not going to happen in 2017. A sub-3.00 season is well within reach, though.

Believability: Pretty high

Dylan Bundy of the Baltimore Orioles is the right age for a breakout, so fantasy owners probably are confident in his 2.97 ERA. However, he’s a sell-high candidate. His walk rate is down from 2016, but so are his velocity and strikeout rate. He also has been lucky, with a .259 BABIP and a low home run rate. This isn’t as much a breakout as it is a small sample anomaly. He has improved, but a sub-3.75 ERA the rest of the way is a stretch.

Believability: Low

Mike Leake of the St. Louis Cardinals is second in the National League in ERA. He was terribly unlucky in 2015 and has turned that 180 degrees this year: His low BABIP and home run rates are driving performance.

Things will reverse some as the days get warmer. He’s still a decent pitcher — just not a great one.

Believability: Better than Bundy’s, but not by a whole lot

Ivan Nova appears to be another Pittsburgh Pirates/Ray Searage salvage job, but all is not quite as good as it appears. He remains a low-strikeout pitcher with marginal ground-ball rates, so his ERA upside lies around the 3.50-3.75 range. He has been lucky, and that’s due to run out.

Believability: Low

Lance McCullers of the Astros looks like a legit breakout. His performance is perfectly aligned with his skills — 9.9 strikeouts per nine innings and 4.0 K/BB.

He’s a potential No. 1 starter and is showcasing it. One thing to be aware of is his injury risk; he missed 100-plus days in 2016 with shoulder and elbow troubles. We’ll bet on his health for now.

Believability: High

Alex Wood is a good pitcher who has taken his game to a new level with the Los Angeles Dodgers. After battling injuries last year, he’s throwing as well as he ever has. He has added 4 mph to his fastball since 2015 and his ground-ball rate has taken off (currently an astonishing 68%). Like McCullers, there’s injury risk. Even so, he’s a horse you should ride as long as you can.

Believability: High, though not quite as high as McCullers’

The Disappointments

Corey Kluber of the Cleveland Indians hasn’t pitched anywhere near as badly as his 5.06 ERA would indicate. His back issues might be contributing, but an elevated BABIP (.320) and a high home run rate are the real culprits. With health and better luck, he could return at least to his 2015 form, and maybe even approach 2016’s.

His back injury is a concern, so don’t discount that.

Believability: Low

Jon Lester of the Chicago Cubs is a mixed bag. His ERA is a run higher than last year, though he benefited from low BABIP in 2016. His walk rate is up, and that’s bigger concern. The biggest difference in his value from 2016 is the 19 wins then vs. two so far in 2017.

In time, the wins might correct themselves, though “in time” could mean 2018. He’s not 2016 Lester, but he’s still a 3.50-ish ERA pitcher with a strong offense behind him

Believability: The precise midpoint between high and low.

Justin Verlander of the Detroit Tigers is getting killed by his walk rate, and the underlying metrics say it’s mostly bad luck.

His BB/9 should be closer to 2.5-3.0, not his current 4.29. Once the walks correct, he should be in line for something like a 3.75 ERA. He’s not done yet.

Believability: Moderately low

Johnny Cueto’s results were better than his skills would indicate with the San Francisco Giants in 2016. But his current 4.50 ERA is an over-correction. Yes, his 2.5 BB/9 rate is higher than it has been in several years, but with strikeouts holding steady, it’s still very good.

The main question is whether he has lost his ground-ball touch: After a 50% rate in 2016, he’s down to 39% in 2017. Unless he can figure that out, he’ll flirt with a 4.00 ERA the rest of the way.

Believability: Somewhat

Kyle Hendricks of the Cubs was fortunate in 2016, and while his 2017 hasn’t been horrible, he’s still well below his 2016 value. His walk rate has shot up at the same time strikeouts and velocity are down in 2017, which is never a good combination.

Hendricks is performing better in 2017 than we would expect given his skills, meaning there’s additional downside, not upside, here.

Believability: Low