ST. LOUIS -- If you're looking for numbers to explain what Jose Martinez is doing, why he's doing it here and just how big of a grain of salt his white-hot start should be taken with, one in particular stands out.

That's the exit velocity reading from his clothesline-like solo homer on April 12 against the Reds, a seared 113.7-mph shot that sent fans scurrying for cover beyond the left-field wall. The radar says more than the Cardinals first baseman's .329/.409/.526 slash line, basically because it suggests those numbers are real. And more than any other swing of Martinez's brief big league career, that big one in Cincinnati offered the best snapshot of why St. Louis' front office targeted him three years ago, and how they essentially found a middle-of-the-order bat on the baseball equivalent of the clearance aisle.

"He just hits the ball hard," manager Mike Matheny said, emphasizing the adjective and needing no further explainer.

It's an Occam's razor-type answer, but not an incorrect one -- 113.7 mph home runs are Giancarlo Stanton hard, Aaron Judge territory. It's a zip code only one other Cards hitter visited in at least the past three seasons. The other, Marcell Ozuna , cost a bundle of four prospects to acquire. Martinez required only cash, and a relative morsel of it, after the Royals designated him for assignment in 2016.

"It was one of those kind of deals that seems small at the time," general manager Michael Girsch said. "But every now and then, you hit big on one of them."

Cardinals officials first eyed Martinez a year earlier, when he was swinging his way to a Pacific Coast League batting crown for Kansas City's Triple-A affiliate in Omaha. He hit .384/.461/.563 that season, his 12th in pro ball without a big league taste. The breakout year failed to make a major prospect out of Martinez, who by that point was 26, had cycled through three organizations, undergone three knee surgeries and never hit for power. Back home in Venezuela that winter, he wondered what he still had to prove.

"My mom was there," Martinez said. "And she said, 'You did everything you can do to be a big leaguer, so don't stop now.'"

Meanwhile, the Cards saw sleeper potential oozing out of Martinez's 6-foot-6 frame, specifically the batted-ball numbers it sent simmering onto their Trackman screens.

"The data supported the fact that he hit the ball really, really hard. The .380 wasn't a fluke," said Girsch. "But he didn't elevate a ton. You could see that by his launch angle and you saw it in his stats."

To the Cardinals, Martinez profiled as a prime depth candidate to bolster a Triple-A Memphis roster set to graduate Tommy Pham, Randal Grichuk and Stephen Piscotty . If pushed, maybe he could help the big league club as an ancillary piece. Then the Royals, their roster stuffed and on their way to a World Series, didn't promote Martinez that September.

"That's when we started to realistically think he might actually hit free agency," John Vuch, who oversees the Cards' acquisition of Minor League free agents, wrote in an email. "Up to that point, I think we all assumed he'd wind up on the Royals' 40-man roster. … I was ready to contact his agent as soon as the bell rang for free agency."

The Royals protected Martinez by adding him to the 40-man late on the final day to do so, less than a week after beating the Mets in the World Series. They designated him for assignment the following May to clear space for Whit Merrifield, at which point the Cardinals pounced.

"We were confident he could be a good right-handed hitter off the bench. That's what we thought we were getting," said Girsch. "Since then, he's been raking."

After altering his swing in an attempt to elevate the ball more ("Ground balls are not allowed!" Martinez says now), Martinez posted some of baseball's best offensive peripherals over a partial season in 2017. This year he's been even better, swinging his way out of questions over his playing time and into the No. 3 spot in the Cards' lineup. Martinez leads the club with 29 hard-hit balls (defined by Statcast™ as exceeding a 95-mph exit velocity), which he's dispersed indiscriminately: 14 on hits, 15 on outs. The hard outs means he is actually underperforming his metrics, despite his gaudy slash line.

"He may have had more value to a team like Kansas City or anywhere else if more of that data was out there.," Matheny said. "I'd never heard of him, so I've been excited and surprised. The more I watch Jose, the more I realize it's legit."

To find the last Minor League transaction to make such an impact in St. Louis, you have to look at Ryan Ludwick, who hit 84 home runs with the club from 2007-10.

"When you look at his history and the impact he's having on this club, I don't know if anybody could have connected those dots," president of baseball operations John Mozeliak said. "To see where he was a few years ago to see where he is today, it's a pretty cool story. If you think about, most of those stories don't end like this."