For these breakthroughs, I considered:
• Players who were no longer rookies to start 2014.
• Players who either established a substantially higher level of performance, or who established themselves as everyday players/mid-rotation starters when they were previously part-time or extra players.
While many other players had apparent breakouts this year (e.g., Josh Harrison), these 10 players all have had breakouts that I believe are sustainable into future seasons. I picked five starters and five position players.
Pitchers
Unfortunately, Richards' season is over due to a freak knee injury that might put him out of action into spring training of 2015, which hurts the Angels' chances of advancing in the postseason and overshadows what an amazing year he's had. Richards was throwing mostly four-seamers and sliders before this season, which made him vulnerable to left-handed batters and generally to hard contact when he left the fastball up. This year, he added a two-seamer, with more life than the four-seamer (which has some natural cut) and a different look, while also adding a curveball to complement the slider, a pitch with similar shape but lower velocity. Assuming his knee allows it, he'll return to ace status next year.
Arrieta had good stuff with Baltimore, especially in short looks, but had below-average command dating back to his time in college and on the national team, where I first saw him in the summer of 2006. The Cubs have made a practice of going after guys like this to try to unlock some of that hidden value, such as the waiver claim/trade for Jacob Turner earlier this month, and Arrieta is the model. Pitching coach Chris Bosio got Arrieta to take the same kind of controlled, deliberate delivery he'd show in side sessions into games. He's more consistent from start to finish now, with less physical effort (virtually eliminating the head whack he used to have) and more mental composure, too. He's better able to command the fastball, especially in working to the lower corners of the strike zone. He looks like a top-of-the-rotation starter now and has all the physical attributes to maintain it going forward.
Hughes, a former first-round pick who never panned out with the Yankees, signed what I thought was a crazy three-year, $24 million deal with the Twins this offseason, but now the move looks like genius after Hughes turned into the Walk Miser.
His walk rate is less than half of his previous single-season best, and it's two-thirds less than his figure from 2013. Pitching coach Rick Anderson decided not to do too much with Hughes, but addressed his imbalance between his strong glove-side command and unwillingness to pitch inside to right-handers (his arm side) by adding a two-seamer to Hughes' repertoire and getting Hughes to throw his cutter to left- and right-handed hitters. Now that Hughes can hit both corners, it has opened up the plate for him and hitters can't sit on just one side of the zone. His ERA might not even tell us how good he's been: His FIP, 2.61, is fifth best in the AL so far, thanks to the lowest walk rate of any qualified starter in baseball.
Kluber was never a top prospect on any of my lists; as far as I can tell, the only time I ever wrote about him as a minor leaguer was the day that Cleveland acquired him from San Diego. The more fool I for missing out, as Kluber has become one of the AL's top three starters, with a couple of significant adjustments this year to cement his status there and make him a great candidate for a long-term contract. Kluber has one true breaking ball now, the out-pitch curveball, and has ditched his slider for a cutter in the 86-90 mph range that occasionally shows slider-ish depth. The biggest change for him, however, has been the switch from a four-seam grip to a two-seam grip, which gave him better feel for the pitch and thus better command -- as well as, paradoxically, a little more velocity, too. He's a true four-pitch guy, three of them plus, with grade-70 command.
Keuchel's turnaround this year, from up-and-down starter to borderline All-Star, has been pretty well documented, although the way Houston pitching coach Brent Strom managed to turn him and Collin McHugh into viable major league starters has to give the team and its fans some hope going forward. Keuchel used to work with a fringy four-seamer that he'd leave up in the zone and a below-average curveball that did him no favors at all. Now he's sinking the fastball, staying away from the upper third of the strike zone, and his slider is big and sharp and a weapon against left- and right-handed batters. If you don't walk guys (he cut his walk rate by about a third this year), miss some bats and keep the ball in the park, you're going to sit at or near the top of a lot of rotations.
Hitters
Rendon was one of my preseason breakout picks primarily because I thought he'd hit once he had more playing time behind him, since he's missed so much time in his college and pro careers due to ankle injuries. This past offseason was also the first one he'd had in several years that didn't see him rehabbing from one of those maladies, meaning he could concentrate instead on getting stronger and adding some muscle mass. It also appears to have helped him to get back to his natural position of third base, where he's an above-average defender and no longer has to go through the kind of on-the-job training he had at second base in 2013. He's an incredibly calm, even-keeled player, and has been a rock in the Nats' lineup in a year when they've missed a number of their more famous hitters due to injuries, not least of whom is the man Rendon has had to replace -- Ryan Zimmerman.
Gomes came over in a deal for reliever Esmil Rogers, a trade that seemed forgettable at the time Cleveland and Toronto made the swap. When he was in the Jays' system, Gomes never had the chance to catch every day, so it appeared that at best Cleveland had acquired a utility guy who could back up behind the plate. But he told the club he wanted to work on his defense, skipping the World Baseball Classic even though he's the best position player ever to come out of Brazil, and instead going early to Goodyear to work with Kevin Cash and Sandy Alomar Jr. The offensive profile hasn't changed much, but what's ordinary at first base is All-Star caliber when you combine it with above-average defense, and Gomes does that with his receiving and his throwing -- and he's even getting stronger as this season, his first full season as a catcher, has progressed.
Brantley's story is a simpler one -- he got stronger, but just a little later than most hitters do. Brantley's always had a lean, athletic body with a line-drive-oriented swing, and rarely swung and missed as a prospect or even as a subpar major league hitter.
His dad, Mickey, had a stouter build, but as recently as last year it didn't look like Michael would develop into more than a contact/doubles guy. He's added some muscle this year, at age 27 -- long considered the peak age for hitters, although those curves may be shifting -- so while his BABIP is unchanged, he's already set a career high in homers (with a HR/fly ball rate over twice his career best) and is on his way to doing the same in doubles. He may not be a 20-plus homer guy going forward, but I'll buy 15-20 homers with 40 doubles from him for the next several years.
Eaton's been hurt on and off this year, a function of his all-out playing style (you might even call him "gritty"). The assurance of a regular job that will still be there for him when he gets back from the disabled list has helped, but more importantly the White Sox have let him be the hitter he is: a very tough at-bat, a guy who likes to work the count even if it doesn't produce huge walk totals. With Arizona in 2013, Eaton was in a vicious cycle where he had to perform right away to get or stay in the lineup, but was encouraged to be more aggressive at the plate -- and that's not his natural approach. This is why scouts and execs often argue that a change of scenery might help a player, and in Eaton's case it certainly has.
Rizzo was on my honorable mentions list for breakouts this spring, but that was before I knew that he'd spent time working out with Joey Votto this offseason -- and Rizzo has done a pretty fair Votto impression himself over the course of 2014. He's become a more precise hitter, still very disciplined, but also more effective at squaring up pitches in the zone that the majority of hitters don't hit. His high walk rate from April/May hasn't held -- although I think he still has that 100-walk capability in him -- but his power increase has, and he looks like a perennial 30-homer guy going forward.
Honorable mentions: Chris Archer, Jake Odorizzi, Jose Quintana, Kyle Seager, Dee Gordon, Jonathan Lucroy