As a shortstop in the Dominican Republic three years ago, Sanchez finished infield reps at a Phillies workout just in time for a catcher -- the main event -- to take batting practice. But there was no one to pitch to the catcher. So Sanchez took the mound.
When all was said and done, the catcher went unsigned. Sanchez did not.
But one man, maybe the one you'd most expect to be let in on the secret, had not heard.
By the time Edgar Cabral learned Sanchez's tale, he had felt the pop of Sanchez's easy 100-plus mph fastballs and seam-ripping curveballs more than anyone. Yet he, of all people, was left in the dark until a couple of weeks ago.
"Sixto was the one that told me," Cabral said.
Just three years ago, Sanchez wasn't pegged as a future All-Star pitcher with top-of-the-rotation stuff. Instead he was fielding grounders, standing some 40 feet from the dirt hill atop which he'd soon pave his path to the bigs.
Cabral, his catcher, was sent up to Class A Clearwater a week ago. On Friday, Sanchez was called up to join him.
"This year he's blossomed," said Cabral, who caught Sanchez's first 12 starts. "He's got a power arm, it's live."
Before his callup, Sanchez had a 64/9 strikeout-to-walk ratio. If he hadn't missed time with a neck injury, his 0.82 WHIP would be best in the South Atlantic League and his 2.41 ERA would rank second.
As if 102 mph and two-plus off-speed pitches wasn't enough to overwhelm opposing hitters, Sanchez works at a breakneck pace.
"I play with the timing of the hitters pitch by pitch," Sanchez said through Gustavo Armas, a BlueClaws pitcher who translated.
In his last start in Lakewood, throwing to Cabral, Sanchez clocked in at 102 mph against the game's first batter. To begin the second? Three fastballs. Three strikes. Twenty-eight seconds. Major League starters average 24.7 seconds between pitches this season. There are a handful of relievers who take more time between pitches than it took Sanchez to strike out one hitter.
"There were quite a few times this year where he was already ready to pitch when I gave him the sign and the hitter isn't ready," Cabral said.
The man Sanchez modeled his attitude after, long before ever taking the mound, was his idol, Pedro Martinez. Last October, Martinez tweeted, "As a pitcher, a quick worker can get the game going; it disrupts the hitter's timing."
During the peak of his career, Martinez spoke of taking the mound and thinking you're unbeatable from start to finish, one massive disruption to a hitter's faculties. Not trying to be better. Knowing you're better. And it showed.
"I liked his behavior," Sanchez said of Martinez.
Sanchez's frenetic pace is a disruption, so much so that he's thrown his allotted five to six innings and allowed two or fewer runs in 20 of his 24 starts in Rookie League and Class A, with a 1.55 ERA and 0.79 WHIP. His last start with Cabral was only his second of those 24 in which he walked multiple batters.
Scarily enough, he's getting even better. Just ask the man who, now fully let in on the secret, knows better than anyone.
"He got smarter with delivering his pitches," Cabral said. "It's definitely amazing."
Ben Harris is a reporter for MLB.com based in Philadelphia.