Brad Keller just finished one of the best rookie seasons ever by a Royals pitcher

For the last month and a half, rookie Ryan O’Hearn has been the talk of Kansas City baseball. And if not for Patrick Mahomes obliterating the world as we know it, he might have been the talk of Kansas City sports. When you slug at a .638 clip through 38 games with a .360 ISO, that will usually get people talking. However, while O’Hearn has burst onto the scene unlike any Royals rookie we have ever seen, he isn’t the best rookie on this team.

That position belongs to Brad Keller, who will likely see far fewer column inches devoted to him this offseason than the likes of O’Hearn. Last week, I talked about the unprecedented power of O’Hearn. While the first baseman has set the world on fire, Keller has continued his slow, methodically, and unflashy rise to the top of the American League WAR leaderboard for rookies.

At 3.6, Keller trails only Shohei Ohtani’s 3.8 mark in bWAR and is ahead of players such as Gleyber Torres, Miguel Andújar, and Lou Trivino. He also has the edge over NL contenders Juan Soto, Walker Buehler, and Jack Flaherty.

But most people don’t know that. In fact, if you asked most baseball fans to talk about that one rookie in Kansas City who is having a Rookie of the Year caliber season, most would probably remind you that O’Hearn has only played in 39 games.

Or, they just simply don’t care. In Jim Bowden’s 2018 Rookie of the Year Tracker ($), Bowden lists Keller as one of the “other top AL rookies,” outside the top five, and even then, Keller is just the third pitcher mentioned. When that was written, Keller led all AL rookies in rWAR, the first stat cited by Bowden for every rookie.

In reality, Keller won’t get much attention for the AL Rookie of the Year, and although I think he is getting a bit of a raw deal, I’m not going to die on that hill. fWAR tells a slightly different story, with Keller being worth 2.5 wins, and I have always been a bigger fan of fWAR.

But, we shouldn’t forget about what Keller has done and against what odds he has done it against. The Royals have a history of diving headlong into the Rule 5 Draft pool and it netted them arguably the greatest Rule 5 pick in history in Joakim Soria back in 2006. They also snagged Nate Adcock in the 2010 Rule 5 draft, who had a 2.34 ERA in 2012 and signed my hat at Busch Stadium, which should count for something.

They did it again this season with Keller and Burch Smith, this time via trade with the Reds and Mets. While Smith has been less than stellar, the Royals had liked Keller since 2013, when they almost drafted him and he has shown why. And although Keller hasn’t blown hitters away, he has put together one of the best seasons in Royals history for a starting pitcher.

And with Ned Yost telling the media that Keller’s victory over the Tigers on Sunday would be his last start of the season, we can now look at how his rookie season compares to other rookie starting pitchers.

Only 17 American League rookies since 1970 had a lower ERA than Keller’s 3.08 mark and only two of them — Paul Splittorff and Bob Johnson — were Royals. That 3.08 mark was aided by a piping hot September where Keller looked as good as he has looked all season from the mound. In three of his last four starts, Keller went 7.0 and gave up just one run. His ERA for the month came in at a cool 2.33.

While Johnson’s 4.5 rWAR was better than Keller’s this season, Split’s fell just short. If we’re going strictly by WAR, only Johnson and Kevin Appier had better rWAR’s as rookies than Keller. Keller’s 3.6 mark was better than guys like Tom Gordon (3.3 rWAR, 3.64 ERA, 153 SO) and Yordano Ventura (3.2 rWAR, 3.20 ERA, 159 SO).

And he has done it with one really good pitch. Keller has thrown a fastball/sinker 70% of the time, a mid-90s offering that has been one of the best in the league. Only eight pitchers have a higher rated fastball according to Fangraphs than Keller’s, which came in at 17.8 runs above average.

One of the reasons Keller’s season and his dominant fastball haven’t gotten as much attention as they should is because they haven’t produced strikeouts. Chicks dig the long ball, but in today’s day and age, they also love the strikeout. Keller’s K/9 is the 7th worst in baseball among pitchers with at least 140 IP, while his sinking fastball has produced the 2nd highest groundball percentage in baseball.

Groundballs have gotten Keller outs and have made him one of the best rookie pitchers in baseball, but they aren’t sexy. They also aren’t an increasingly sustainable form of success. While there have been many pitchers who have made a living off of the ground ball, none of them have done it with the K-BB% numbers that Keller has put up. In 2018, Keller’s 7.9 K-BB% is the 4th worst in the league. He is the only pitcher in the bottom 10 with a sub-4.00 ERA and is one of two pitchers in the bottom 27 with a sub-80 ERA-.

Back in June, Paul Sporer of Rotographs wrote about Keller’s success and said, point blank, that “Keller’s ERA is going up at least two runs” from its current 2.45 mark. He was wrong then, but it’s fair to be skeptical of whether he isn’t right going forward.

There are a lot of question marks surrounding Keller’s ability to maintain this level of success and we will almost certainly see some sort of regression in 2019, if not a major one. But that doesn’t change that his 2018 campaign will go down as one of the best ever for a Royals rookie. The odds are stacked against him to continue that success, but that isn’t anything new for Keller.