Let's take this time to seek out 2017's likeliest breakout pitchers, but first we must answer the surprisingly complicated question of "what makes a breakout season?"
For example: Kyle Hendricks cut his ERA nearly in half from 3.95 to 2.13 and finished third in the National League Cy Young Award ballot. Yet while the run prevention was markedly better, the inputs behind it -- strikeouts, walks, homers -- didn't change much. (There was even evidence he induced less soft contact than he had in 2015.) Of course, Hendricks did find himself in front of one of the best defenses in history, which helped save runs.
So if a breakout season means that the pitcher was hugely different, Hendricks wouldn't qualify. If it means that the overall success rate was different, then he surely would. That's the definition we'll use here, identifying pitchers who -- either due to changes they've made or changes made around them -- could be in position to allow fewer runs in 2017.
Robbie Ray, Diamondbacks
Why: Arizona is going to make it easier on their pitchers to succeed

Ray had himself a pretty odd 2016 season, as advanced metrics liked him (3.0 FanGraphs WAR, where 2 is "league average") due to his high strikeout total, but traditional numbers (8-15, 4.90 ERA) most certainly did not. The reason few worry about pitcher win/loss record any longer is because that reflects the quality of the team, not just the individual, and in this case, that approach applies to Ray's run prevention issues as well.
Remember, the D-backs had a solid defensive outfield in 2015, with David Peralta and Ender Inciarte flanking A.J. Pollock. But in 2016, Inciarte was in Atlanta, while Peralta and Pollock missed huge chunks of time due to injuries, leaving Arizona to play converted infielders like Brandon Drury, Rickie Weeks Jr. and Yasmany Tomas in the outfield. The results weren't pretty -- Arizona's outfield Defensive Runs Saved dropped from +37 to -19, a difference of 56 (!) runs.
Inciarte isn't coming back, but simple outfield health ought to make that better on Arizona's staff, not to mention swapping out the framing-challenged Welington Castillo (-10 runs, per Baseball Prospectus) for Jeff Mathis (+8 runs in part-time play). Ray had the fifth-highest strikeout rate among any starting pitcher last year; missed bats plus better defense plus more called strikes can only help.
James Paxton, Mariners
Why: We already saw signs of it -- if he can stay healthy

Dig Paxton's innings pitched totals and strikeout / walk numbers the last three seasons, particularly the difference between his strikeout and walk rates.
2014
74 IP -- 19.5% K% -- 9.6 BB%
2015
67 IP -- 18.9 K% -- 9.8 BB%
2016
121 IP -- 22.9 % -- 4.7 BB%
See that? Paxton doubled his innings pitched, cut his walk rate in half and increased his strikeout rate. Paxton was one of just three lefties to touch 100 mph last year, and really, anyone who manages to whiff Michael Trout four times in one game deserves a little respect. He did land on the disabled list again, but at least this one was more of a fluke incident, having been hit by a line drive.
Though some already think Paxton has arrived, his 6-7, 3.79 season make it clear that the "true" breakout might be one season away. Between the velocity, the improved secondary pitches, and the step forward in throwing strikes, there's a lot to like here.
Jon Gray, Rockies
Why: A fastball/slider pitcher who can miss bats can beat Coors Field

Any pitcher who calls Coors Field home is always going to have more to overcome than others at more pitcher-friendly home fields; then again, we did watch Gray strike out a team-record 16 while shutting out San Diego in Denver last September. A pretty effective way to make sure that hitters can't take advantage of the thin air and massive outfields is to make sure they don't make contact, and Gray struck out 185 in 168 innings as a rookie.
So that's a good start, as was the fact that Gray actually performed better at home than he did on the road. But why wasn't the overall production there, in a year that ended with a 4.61 ERA? In part because of inconsistency, as he had seven starts where he didn't make it past four innings, but also because a pair of back-to-back August starts where he allowed 14 runs in eight innings.
Gray chalked that up to losing the feel on his slider, and that's a big deal.
"Against the Marlins, the action was so bad, really bad," he said afterward. "It was really flat. It didn't have an effect at all. It was an easy, hittable pitch."
That's a big deal, because Gray's slider is his best pitch (.180 average against), and had the 11th-highest whiffs per swing rate of the 103 pitchers to throw 200. When the slider is there, as it usually is, he's quickly becoming one of the NL's better starters.
Marcus Stroman, Blue Jays
Why: He started using his pitches more effectively

Stroman's breakout feels about two years overdue, as it seemed like it was going to happen in 2015 before he injured his knee in Spring Training and missed nearly the entire season. He pitched 204 innings in 2016 and proved he was healthy, but he was just fine, and not much more -- less, even, if you buy into that 4.37 ERA.
But there was also evidence of improvement as the season went on. For a high-level view, just look at Stroman's monthly ERA:
April -- 4.37
May -- 4.54
June -- 7.76
July -- 3.71
August -- 3.13
September -- 3.41
What happened? Well, Stroman's first-half strikeout rate jumped from 17 percent to 23 percent, while his walk rate dropped slightly. That happened due to a change in pitch mixture, as he started throwing his sinker less and less in favor of his slider and cutter. Interestingly enough, his high groundball rate -- highest of any starter -- didn't suffer with fewer sinkers, because his slider gets them too. There's also evidence that Stroman's pitches move into relation to one another like no one else's in baseball.
If you have a pitch that gets grounders and misses bats, use it. Stroman took that advice, and it showed.
Blake Snell, Rays
Why: Always bet on hard-throwing lefties with multiple pitches 

In an up-and-down rookie season, Snell struck out 98 in 89 innings, which is a nice introduction. He also had a 3.54 ERA and had a too-high 12.7 percent walk rate, which is a nice reminder that pitching in the bigs is really, really hard.
Still, we saw a lot to like. Remember above, when mentioned Gray's slider rated highly on the whiffs-per-swing list? You might say Snell's pretty high on that list, too -- he's No. 1. We also saw a lot of that high-spin fastball, which had the third-highest spin of the 89 lefties to throw at least 100 of them. High spin is positively correlated with swinging strikes, though Snell was a bit too wild with it to gain as much value as he could have.
Snell needs to prove that he can improve his command. But any time you can start with a high-spin, high-velo fastball, and an improving slider that might be a really good pitch, you're doing something right. Similar to Ray above, a full season of health from center fielder Kevin Kiermaier would help here, too.
Bonus pick: Julio Urias, Dodgers
Why: He's so young and already so good

We're including Urias here to briefly remind you that in his age-19 season, he had a 3.39 ERA and a 3.17 FIP, and if you look past his poor first two outings, those numbers were 2.73 and 2.60. That's basically what Johnny Cueto was in 2016, but better. Urias isn't going to give 200 innings in 2017 as the Dodgers manage his young arm, but you can easily argue the breakout already happened as soon as he set foot in the Majors. He's that good.