Rockies Gamble on Anderson's Wicked Slider

After watching a generation of pitching prospects mostly go bust, the Colorado Rockies have started to cobble together what could be a quality rotation with ground ball-generating starters Jorge de la Rosa, Jhoulys Chacin and Tyler Chatwood in the majors and Eddie Butler and Jonathan Gray on the farm. The Rockies added another high-upside worm-burner on Tuesday, acquiring Brett Anderson and cash from the A's for one of those stalled young arms (Drew Pomeranz) and minor leaguer Chris Jensen.

Anderson, 25, devolved from Oakland's ace-in-waiting to a training table regular thanks to an elbow injury that eventually required Tommy John surgery in 2011 and a stress fracture of his right foot that wiped out most of his 2013 season. The last time the former Diamondbacks prospect tossed even 100 innings was 2010. But Anderson has been tantalizing when able to take the mound, limiting walks (2.4 per nine innings pitched) and churning out ground balls (55 percent of pitches put in play) while compiling a park-and-league adjusted ERA that's nine percent above the league average.

The lefty's slider is a major reason why he has tormented hitters when not on the rehab trail. Anderson has thrown the sweeping, low-80s pitch more than a quater of the time (26.2 percent) during his MLB career, limiting hitters to a .270 slugging percentage. That's tenth-best among starters since 2009, right behind slider aficionado Francisco Liriano.

Why is Anderson's slider so deadly? He gets hitters to pound the pitch into the grass, and he grabs lots of called strikes by freezing opponents on sliders thrown over the plate.

Take a look at Anderson's ground ball rate by pitch location with his slider (left), compared to the league average for left-handers:

Overall, lefty starters had a 46 percent ground ball rate when throwing a slider from 2009-13. Anderson induced grounders 66 percent of the time with his slider, tops among all southpaws who regularly throw the pitch by a wide margin (Jaime Garcia is a distant second, at 60 percent).

When Anderson isn't getting grounders with his slider, he's jumping ahead in the count as hitters take breaking pitches thrown over the plate. Opponents have swung at just 57 percent of the sliders that Anderson has located within the stike zone, far below the 66 percent average for left-handed starters. With hitters gluing the bat to their shoulders, Anderson has the fourth-highest called strike rate (36 percent) with his slider among lefties since '09, trailing just Chris Sale, Ted Lilly and Mike Minor.

Coors Field and breaking balls go together like peanut butter and motor oil, but research suggests that sliders aren't harmed as much by the mile-high air as curveballs. Plus, the Rockies have paired ground ball-centric starters like Anderson with quality infield defenders (Colorado converted the sixth-highest percentage of ground balls put in play among MLB clubs in 2013). If Anderson is ambulatory, he could be a major bargain at a net $6 million salary next year and stick with the Rockies through 2015 (the club holds a $12 million option). When you're desperate for premium pitching, taking a chance on an oft-injured potential ace can't hurt.

Drew Pomeranz Has a Split Personality

The A's and Rockies exchanged lefty lottery tickets at the winter meetings, with Brett Anderson (and $2 million cash) headed to Colorado for Drew Pomeranz (and minor leaguer Chris Jensen). From Oakland's perspective, trading the oft-injured Anderson saves at least $7.5 million (his $8 million salary in 2014 minus the cash sent to the Rockies, and a $1.5 million buyout on a 2015 club option) and gives the A's team control over a former top-five draft pick through the 2018 season.

GM Billy Beane said the deal allows Oakland to "turn back the clock a little with another very talented left-hander," letting the club's development staff tinker with Pomeranz' herky-jerky delivery in hopes of unlocking the talent that made him a top-25 prospect and the key player acquired by Colorado in the 2011 Ubaldo Jimenez deal. The problem is, the 25-year-old's development clock is frozen in time -- he's still a fastball-first pitcher with unreliable secondary stuff, leading to gargantuan platoon splits.

During his major league career, Pomeranz has suffocated fellow left-handed hitters to the tune of a .457 on-base-plus-slugging percentage. No lefty starter in the game has a lower OPS against same-handed batters over the past three seasons (minimum 100 lefties faced). Against righties, though? Pomeranz has been pummeled for an .888 OPS, topping only the now- unemployed Jonathan Sanchez (minimum 400 righties faced). Basically, Pomeranz turns lefties into Felix Pie and righties into Matt Holliday. That's a problem when about 56 percent of the major league population swings from the right side.

Here's a closer look at what makes Oakland's new reclamation project deadly versus lefties, and dead in the water against right-handers.

Lefty Killer

Among left-handed starting pitchers facing at least 100 lefties over the 2011-13 seasons, only David Price and Tony Cingrani (80 percent each) threw fastballs more often than Pomeranz (79 percent). Pomeranz pounded the outside corner versus left-handers, throwing far more heaters to the outside corner (61 percent) than the MLB average (48 percent). Pomeranz's simple approach -- play keep-away with the fastball, and mix in an occasional curve -- paid off handsomely.

• Pomeranz has eviscerated fellow lefties with his fastball, inducing whiffs at an elite level. Left-handers have missed 34 percent of the time they have swung at Pomeranz' heat, highest among all lefty starting pitchers throwing at least 400 fastballs to same-handed hitters over the past three seasons. His fastball miss rate is nearly double the MLB average for lefty-on-lefty matchups (18 percent).

Pomeranz's fastball contact rate vs. lefties, 2011-13

• Many of those whiffs from lefties are coming on pitches thrown off the plate. Batters have chased 34 percent of Pomeranz's fastballs located outside of the strike zone, also the highest among lefty starters taking on same-handed hitters. The MLB average? just 24 percent.
• By generating so many whiffs and chases, Pomeranz boasts the highest fastball strike percentage against lefties (70.6) this side of Cliff Lee (73.3).
• Pomeranz has also spotted his curveball against same-side batters, throwing a strike 59 percent of the time (58 percent average for lefty vs. lefty confrontations).

Righty Punching Bag

Lacking a reliable changeup, Pomeranz threw the highest percentage of fastballs to righties (77) among all lefty starters taking on at least 400 opposite-handed hitters from 2011-13. He tried to bust right-handers in on the hands with his fastball, throwing inside 42 percent of the time (34 percent average for lefty pitchers). Clayton Kershaw (47 percent) was the only lefty to challenge right-handers inside more frequently. Kershaw, possessing 93-97 MPH gas and a pair of wicked breaking pitches, can get away with that. Not so much with Pomeranz, who complements his low-90s fastball with spotty secondary stuff.

• Batters swung through Pomeranz's fastball 15 percent of the time -- a dead ringer for the MLB average in lefty versus righty matchups. He has actually managed to garner more chases with his fastball (30 percent) than the MLB average for lefties against righties (24 percent).

Pomeranz's fastball contact rate vs. righties, 2011-13

• While his fastball is modestly effective versus opposite-handed batters, the same can't be said for his curveball (thrown 15 percent of the time) and changeup (8 percent). Over the past three seasons, Pomeranz has the lowest strike rate with his curveball (47 percent) among all lefties throwing at least 250 benders to right-handed hitters.
• His changeup strike rate is even lower (43 percent). Cingrani is the only lefty to miss the mark more often with his changeup against righties (minimum 100 thrown).

The A's have a full rotation, with newly-signed Scott Kazmir joining Jarrod Parker, Sonny Gray, A.J. Griffin and Dan Straily, so Pomeranz figures to start 2014 attempting to conjure up breaking and off-speed stuff at Triple-A Sacramento. Short of accomplishing that, this former bonus baby could be headed for a career as a lefty specialist out of the bullpen.