PHOENIX -- Imagine if the difference between fulfilling the lifelong dream of being signed by a Major League team or going home to regroup was a single second on a stopwatch during a timed 60-yard run.

A time of 6.9 seconds in the 60 is considered the average for Major Leaguers, and it's an impressive mark for an international teenage prospect. Anything below that number is considered above average. A prospect better be a catcher or able to hit the ball consistently and with lots of power if he runs it closer to eight seconds than seven.

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Marco Luciano, 17, who ranked No. 3 on MLB.com's Top 30 International Prospects list and is now the Giants' No. 5 prospect, has been running a 6.7-second 60 for two years, and it's not even his best attribute. His power and his arm can claim that distinction. The combination of those three tools made him one of the most coveted prospects on the market this year and the reason why the Giants signed him for $2.6 million on July 2.

And while the teenager from the Dominican Republic is a rare talent, his story of perseverance is common for international prospects chasing their big-league dreams. Like thousands of others, Luciano was once judged on his ability to hit, hit for power, throw, run and field at the tender age of 15. Now, it's time to fulfill the promise.

"I feel like my best tool is that I work hard," said Luciano, who is currently training at the club's Spring Training complex in Scottsdale. "I come from a humble place and I made it here with my family's support. They are not always by my side, but we are always in contact all of the time and stay in touch. They are everything to me."

Luciano was discovered by trainer Edwin "Ray" Castillo in the northern part of the island known as Cibao in a tryout when he was 12. The infielder, who is 6-foot-2, 180 pounds, was tall and wiry even back then. His skills were advanced for his age, and he was growing so fast that Castillo wondered if Luciano would end up as a corner outfielder with power.

"Life before I signed was hard, but I loved the challenge and it was my dream," Luciano said. "I was up very early and at the ballpark every day until about 1. I would nap until 4:30 and go to the gym. By 8 p.m., I was eating and showering, going to bed and getting ready to do it all over. We rested on Saturdays and Sundays, but sometimes it was just Sunday."

The Giants' international scouting staff first spotted Luciano sometime between his 14th and 15th birthday and made him a top target. The club was immediately impressed with his body and athleticism. They loved his makeup. Giants scouts joke it was love at first sight.

"You can tell he's 17, but you look at his body and face, the way he moves, and the way his actions are, and you can see he is pretty special to say the least," said David Bell, the Giants' director of player personnel. "Obviously, there's a lot of development between now and the Major Leagues, but what a great start this kid has. You can tell he just really enjoys playing and it's our job to make sure he never loses that."

International prospects like Luciano that signed during the period that started July 2 are not eligible to participate in the Dominican Summer League until 2019. Instead, the prospects work out at the team academies in the Dominican Republic and play against recent signees from other clubs. The Instructional League in the Dominican Republic that started earlier this month is often the first real taste of professional baseball for most of the recent signees. Clubs have also been known to send their new international prospects to their Spring Training facilities in Arizona and Florida to introduce them to life in the United States as a professional athlete.

"We care about the whole person," Bell said. "On the international side, we have great educators who help them in the classroom and help them learn to speak English. We also help them physically with their nutrition and strength and conditioning. There are a lot of parts. What we like to think we've been able to do -- and I think we have -- is just bring it all together so we're all working together."

Luciano, who was slowed by a hernia operation last month, expects to stay at the club's complex in Arizona until the middle of October. He's returned to the gym but has not resumed baseball activities.

"You can say life is easier in some ways without the pressure of having to sign anymore, but I know it's going to get more challenging on the field and I'm ready for it," Luciano said. "I'm preparing my body and mind to be strong in 2019. I believe I have a big future ahead of me and that's why I work hard."

Jesse Sanchez, who has been writing for MLB.com since 2001, is a national reporter based in Phoenix. Follow him on Twitter @JesseSanchezMLB and Facebook.