Angels pitcher Robert Coello's mystery pitch leaves hitters muttering under their breath

When considering a name for the pitch he rescued from extinction, Los Angeles Angels reliever Robert Coello at first settled on its historic label: a forkball, jammed deep between his index and middle fingers and released, amazingly, with next to no spin, like a knuckleball. Such an incredible pitch, of course, deserves a far greater name, so Coello has settled on the three-letter acronym that ballplayers blurt when he unleashes it.

"The WTF," Coello said. "Catchers call it that. Hitters say it."

Any other reaction would not do justice to this freakish marriage of grip-fiddling, arm speed and inexplicable physics. Baseballs are capable of miraculous feats: sizzling on a line at 100 mph, dive-bombing when held along the seams, jutting a foot in 10 feet. Now, as the 28-year-old Coello is showing, one need not grip a ball using finely manicured fingernails to make it dance like Beyonce, a thing of beauty going in whichever direction nature desires.

The WTF is not the gyroball. It does not exist in theory. It is not some trick pitch, either, held differently than all the others. Plenty of pitchers around baseball use some sort of a split-fingered fastball grip – the split-change, favored by Tim Lincecum and Ubaldo Jimenez, is the most popular – and some even jam it deep between their fingers like the right-handed Coello. The difference comes when they throw it.

[Related: Angels' Mike Trout in duel with Miguel Cabrera in another magical season]

Whereas other pitchers impart backspin on their splitters and the traditional forkball from masters such as old-style fireman Elroy Face had a tumbling effect, a la curveball, Coello's finds a happy medium: When he throws it right, it doesn't spin at all.

Physicist Alan Nathan, a professor at the University of Illinois who studies baseball and has a particular interest in the knuckleball, hadn't ever seen a pitch like Coello's. His preliminary theory on the pitch: His thumb on the underside of the ball exerts backspin, counteracting the tumbling effect his top fingers put on the ball and balancing the torque so perfectly that the pitch has a knuckleball effect with superior speed (around 80 mph).

"A lot of people like to classify pitches by how they're gripped or released as opposed to what they do," Nathan said. "It's a matter of taste, but whatever you call it, this pitch does look like a knuckleball.

"Maybe he's discovered a new way to throw a knuckleball-type pitch."

The discovery first came more than a decade ago at Lake Region High in Eagle Lake, Fla. Coello and his friends always were messing around with knuckleballs. No matter how hard he tried, Coello couldn't throw one. So he tried different grips until he found the forkball and its mystical spin.

One problem: Coello wasn't a pitcher. He caught in high school, at junior college and with Cincinnati, which drafted him in the 20th round of the 2004 draft. The Angels acquired him in 2007 with a better idea: Let the 6-foot-5, 250-pound Coello put his big arm to better use.

"When they converted me to a pitcher in 2007, they wanted me to stick to fastball, curveball, changeup," Coello said. "And I said, 'Well, I have something else.'"

The WTF always was a work in progress. The first one he threw in rookie ball hit the batter. His coaches thought it was a 12-to-6 curveball. While he kept honing the WTF, Coello's big fastball got him to the major leagues with Boston in 2010. He bounced to the Chicago Cubs, Toronto Blue Jays and back to the Angels this offseason.

Over 18 2/3 innings at Triple-A to start the season, he struck out 29, and the Angels' bullpen mess prompted his arrival. Since then, he has been dominant: 10 1/3 innings, six hits, one walk, 18 strikeouts and a litany of confused hitters who can't touch the WTF, umpires who call it a ball when it crosses the middle of the plate, catchers who get bruised by it and technology that cannot keep up with it.

It's true: The algorithm for PITCHf/x, the camera system that captures every pitch thrown, cannot classify the WTF. While Baseball Info Solutions says Coello has thrown it 13.9 percent of the time this season, PITCHf/x has him throwing changeups, curveballs, forkballs and cutters, unsure of what is what.

"When the air flows over the seams, funny things happen and the ball breaks," Nathan said. "I would say that it is something still of an open question as to why the knuckleball is so unpredictable in how it moves. If the ball is thrown with very little spin, it's not going to be terribly predictable by anybody – the pitcher, the catcher, the batter and scientists."

Coello has become a big enough part of the Angels' plans that they're going to lengths to accommodate the WTF. In the bullpen, they've started breaking in the oversized catcher's mitt teams use for knuckleball pitchers. After getting plunked too many times, Angels catchers want at least some margin for error.

"When it's on, it has no rotation at all," Angels catcher Hank Conger said. "And the thing comes in hot."

More than ever, Coello is starting to feel comfortable controlling the pitch. Early in his career, it was too wild. The Cubs didn't give him a big-league shot. An ulnar-nerve injury cut short his time with Toronto. Coello understands he never will command it, the WTF's whims too flighty for that. When he warms up, he'll throw a few in the bullpen, and if they look good, he stops, knowing that if he puts it near the strike zone the pitch will do what it does.

"When you have the right feel and finish, you kind of have an idea," Coello said. "There are other times when I just don't know."

On such nights, Coello can stand back like everybody else marveling at this pitch and utter the only appropriate thing: What the ... well, you know.

Related coverage on Yahoo! Sports:
Photos: MLB commemorates Memorial Day
Matt Kemp flies terminally ill fan to Los Angeles
David Wright delivers when young fan asks for home run
Broadcaster's 'dead soldier' comment on Memorial Day ill-timed