Tampa Bay Rays: Evaluating Nate Karns’ Rookie Year


We can’t just ignore minor league numbers. Anyone who has seen the movie Moneyball  knows at this point that scouting can overestimate players’ true abilities and leave potentially useful players unnoticed. With that backdrop, Nate Karns‘ officially rookie season in 2015 is a very interesting case. We are talking about a pitcher who pitched to just a 5.08 ERA at Triple-A last season delivering a 3.67 ERA in 147 major league innings for the Tampa Bay Rays.

More from Rays Colored Glasses

Entering the season, Karns was going to compete with Alex Colome for the fifth starter job. Then the injuries started and Karns actually ended up being the Rays’ third  starter to begin the year. He certainly didn’t dominate every time out and had serious issues going deep into games, failing to complete 6 innings in 15 out of his 27 starts and being lifted after 5 or less on 10 different occasions. When he was on the mound, however, he tended to be effective and the Rays could not have asked him for anything more than that. We can also say that some amount of that was on purpose–we know about the Rays’ strategy of not letting their starters face hitters three times, and they had as quick of a hook on Karns as they did on anyone.

Was Karns’ success unexpected? Most Rays fans and analysts–and I can throw myself in that group–were pleasantly surprised by his performance, but maybe a little more than they should have been. After all, Karns’ 5.08 ERA from Triple-A belied the fact that his FIP was a more reasonable 4.03 and his numbers were skewed by a few disaster starts. Those games reminded us that Karns occasionally loses command and throws too many pitches down the middle, but maybe we overestimated how often those outings would take place. It could have simply been bad luck that Karns had 6 or 7 such games in one year.

Beyond that, we didn’t know how good Nate Karns’ changeup would be in his rookie season. We knew about his fastball ranging from the low-to-mid 90’s and his excellent hard curveball, but the fear was that he was going to try to imitate Chris Archer and succeed as a two-pitch pitcher. That was going to be a tough proposition given that both of his offerings were worse than Archer’s–his fastball wasn’t as overpowering while his curveball didn’t have as consistently sharp break.

More from Rays News

Instead, Karns’ changeup burst onto the scene and gave him a reliable third offering, particularly against left-handed batters but also occasionally against righties. We are talking about a pitch that he only used 12.67% of the time, but he upped that to 18.27% against lefties and generated strong results when he did throw it. He perhaps couldn’t spot it in the zone as much as he would have liked and kept it up and away too often, but he set it up well enough with his fastball to use it to generate both whiffs and groundballs without giving up much hard contact. It is clearly his third-best pitch and likely would have been worse under heavier usage, but it looked good enough to help him continue to perform well as a big league starting pitcher.

A more concerning trend, though, may be how Karns finished the season. Before moving to the bullpen and subsequently being shut down with right forearm tightness, Karns gave up 9 home runs in his last 9 starts compared to 9 in the 17 he made before that. Maybe that brings us back to Karns’ numbers from the minors–it was only going to be a matter of time until big league hitters would be able to take advantage of his mistakes on fastballs down the middle. If 2014 was Karns experiencing bad luck, perhaps the first half of 2015 was the pendulum swinging the other way.

That is the sort of thinking that would lead us to believe that Nate Karns will be traded this offseason, especially given how much starting depth the Tampa Bay Rays possess. He has great stuff and the ability to be a number three starter in the major leagues, but given his command concerns and the fact that his changeup is good rather than great, he may not have what it takes to be better than that. There is even a plausible scenario where he gets hit hard next year and makes the Rays look brilliant if they trade him.

The other perspective is that Karns isn’t yet done developing as a pitcher and it would be a pity for the Rays to let him go when he may be on the verge of another breakthrough. That is an interesting point, but we also have to remember that Karns turns 28 in November and may not have as much room to mature as the other rookie pitchers in baseball. Karns’ decline may also come more swiftly because of his age, making him a less attractive pitcher to hold onto even though he won’t be a free agent until after the 2020 season.

No matter what the future holds, though, let’s appreciate the work the Karns gave the Rays this season in a year where they especially needed young pitchers to step up. He has done enough to either earn a spot in next year’s rotation or bring back a significant return in a trade, and we can’t possibly be upset with that. People were exceedingly confused when the Rays traded Jose Lobaton are more to the Nationals to acquire Karns, but this season has made it clear exactly what they saw in him. The only important question left is whether he is more valuable as a starter or a trade chip.

Next: Tampa Bay Rays Game 152: Steven Souza Jr. Comes Alive