Will Gerrit Cole Rebound in 2018?

Cole, the Pirates' ace, may be pitching for someone else next season. Will he fare better than he did a year ago?

Free agency, as a rule, does not often provide Major League teams with a wealth of young, controllable starting pitching. Really good young arms are generally team-controlled through their early-to-mid 20s, and by the time they reach free agency, they're either knocking on 30 years old or have passed by that milestone.

The same is true this year. The top free-agent options, Yu Darvish and Jake Arrieta, are both over 30 and expected to command five-to-seven years and more than a $100 million. The mid-tier options, Alex Cobb and Lance Lynn, can be had on shorter deals for less money, but they don't provide top-of-the-rotation talent and will cost a team draft picks as a penalty for signing them.

So teams are looking to trade for those young arms, and one of the names found most often in the rumor mill is Pittsburgh Pirates ace Gerrit Cole. The New York Yankees have long been rumored to be trying to swing a deal for the 27-year-old, but other teams are reportedly in the mix, as well. He's a hard thrower and a misser of bats, with what one would presume are his best years still in front of him.

However, since 2015, when he finished fourth in the National League Cy Young race with a 19-8 record, 2.60 ERA and 202 strikeouts in 208 innings, his numbers have not been as good.

Among other, more basic stats, we'll take a look at his Baseball Reference WAR (rWAR) and ERA+. For ERA+, the higher, the better. If a pitcher owns a 108 ERA+, that signifies that the average ERA in his league was 8% higher than the pitcher's ERA.

Year ERA Innings Walks Strikeouts ERA+ rWAR
2013 3.22 117.1 28 100 111 1.3
2014 3.65 138.0 40 138 99 1.2
2015 2.60 208.0 44 202 149 4.5
2016 3.88 116.0 36 98 107 1.6
2017 4.26 203.0 55 196 101 2.8

Cole missed much of the 2016 season with a myriad of injuries that landed him on the disabled list three different times. That he came back last year healthy and hurled more than 200 innings was a step in the right direction. But as the numbers above indicate, he wasn't nearly as effective as he was two seasons ago, when he was one of the best pitchers in baseball.

His biggest issue was keeping the ball in the yard. He gave up 31 home runs in 2017, far and away the most in his career (he had given up 36 in his previous four seasons combined) and tied for sixth-most in baseball. His home-run-per-fly-ball rate jumped from 6.8% in 2016 to 15.9% last season. It wasn't all bad luck, either, as he put up career-worst clips in hard-hit rate (31.3%) and fly-ball rate (33.7%) allowed.

And lest you think his 4.26 ERA was undeserved, he also posted a fielding independent pitching (FIP) of 4.08 and a DRA (deserved run average) of 4.15.

But there was some good news. His strikeout rate (23.1%) and walk rate (6.5%) were right in line with his career averages (22.8% and 6.3%, respectively), and his average four-seam fastball velocity (96.3 miles per hour) was also right there with his career average (96.5).

However, that fastball was far less effective. In 2015, the heater saved his team 24.2 runs above average (wFB), whereas last year, that number fell to 3.1.

His slider also became a less effective pitch, saving his team 7.6 runs above average in 2015 (wSL), compared to costing his team 1.4 and 1.2 runs above average in the past two seasons. But there was one change to his arsenal that was perhaps the biggest reason for his struggles -- his changeup.

According to Brooks Baseball, Cole had never thrown his changeup more than 12.9% of the time to left-handed hitters in a single season, and that was in his rookie campaign of 2013. In 2015, when he was his most dominant, he threw it only 5.7% of the time. But last year, that number jumped to 16.0%, and when those lefties got a hold of one, they mashed it to the tune of an isolated power (ISO) of .203.

Now, that's not a lot different from his career numbers with the changeup against lefties, but the fact he threw it more often means that .203 ISO against came into play a lot more. Last year, 18 of the 31 dingers hit against him were bombed by left-handers, and his slugging percentage allowed against lefties (.477) was far higher than his career number (.398).

And Cole was not an especially unlucky pitcher last season, giving up a batting average on balls in play (BABIP) of .298, almost exactly the league average (.297), so you can't blame a mountain of bad luck for his struggles.

So what does all this mean for Cole and, by extension, a team that pulls off a trade for him?

Cole gave up a lot of hits last season -- 199, 14th-most among qualified starters -- and while he may not give up as many homers in 2018, the overall increase in dingers in baseball will likely keep that number a bit elevated.

But Cole is young, still throws hard and controls the strike zone. Given a little more luck, some of those hits and homers could turn into outs. If that happens, he should be a stable top-of-the rotation arm once again and bounce back from a down 2017 campaign.