Even casual sports fans know the names of the superstars in pro basketball. There is LeBron, Steph Curry, Kevin Durant, Russell Westbrook, James Harden. But there is one name you may not have heard, mainly because it takes courage and concentration to pronounce it. I'm talking about Giannis Antetokounmpo of the NBA's Milwaukee Bucks. He is 23 years old, a hair under seven feet tall and there are 13 letters in his last name, most of them consonants, so he is usually referred to as Giannis or 'The Greek Freak.' He's called that because he is Greek and is doing things on a basketball court that people have never seen before. And even if you aren't a basketball fan you have to admire his athleticism and a personal story that is one of the most interesting in all of sports. If that sounds like hype, we offer into evidence exhibit number one.

Milwaukee Bucks superstar Giannis Antetokounmpo CBS News

Last month, Madison Square Garden. Bucks versus the Knicks. A stolen pass, a fast break. Watch Giannis on the right.

It was so quick, most people missed what actually happened.

You have to slow it down and watch carefully to notice that the Greek Freak leapt right over a flabbergasted 6'6" defender while catching the ball and stuffing it through the hoop.

The unpronounceable has become the unstoppable.

Steve Kroft: How many steps does it take you to get down the court?

Giannis Antetokounmpo: Full level of the court?

Steve Kroft: Yeah.

Giannis Antetokounmpo: Six.

Steve Kroft: How many from the foul line?

Giannis Antetokounmpo: From the foul-- one, just one. Maybe none. I can just jump from the foul line I think.

His highlights have gone viral on six continents. Already a two-time All-Star, he's listed in the program as a forward, but he plays every position from point guard to center, and leads the Bucks in points, rebounds and assists. This one surprised even Giannis.

Giannis Antetokounmpo: The hike pass that I did between my legs. That was one of the most-- I was like, wow, I-- oh wow, I just did that.

Steve Kroft: Had you ever done it before?

Giannis Antetokounmpo: No.

Steve Kroft: It just came to you?

Giannis Antetokounmpo: It just came.

Steve Kroft: It was a pretty good pass.

Giannis Antetokounmpo: Yeah. It was a really good pass.

But it's his size and his coordination that intimidate. He has a wingspan of 7'3". And his hands, which are a foot long, are thought to be the largest in the league.

Giannis Antetokounmpo: They're huge

Steve Kroft: Wow

Correspondent Steve Kroft compares hand sizes with 'The Greek Freak' Giannis Antetokounmpo CBS News

They allow him to palm or cradle the basketball as if it was an orange. John Henson, Giannis's teammate, has watched it all.

John Henson: He can jump over you, go around you or go through you.

Steve Kroft: And he's only 23.

John Henson: He's only 23. Phew! He's only 23.

If you go back five years, Henson was on the Bucks when Giannis joined as a rookie. Playing in Milwaukee was a much different experience then. The team was lousy and half the seats were empty.

John Henson: It was like a scrimmage out there, you know what I mean. It was a few people in the stands. We could hear our family. Mom could give you advice you know what I mean? It was one of those things. But, now, it, you know, it's loud, it's, it's, it's rowdy in there.

On most nights now the Bradley Center is hopping. Giannis's presence has put the Bucks and Milwaukee back in the national conversation. The breweries that made it famous during the last century are mostly gone, now it's Antetokounmpo.

Peter Feigin: He's an icon in a small city with a global appeal.

Peter Feigin is president of the Bucks. He says Milwaukee may be a small city by NBA standards but Giannis has put it on the world map, giving it a marketing foothold in the global basketball business.

Peter Feigin: He's one of the great five, 10 players in the NBA at this time. And he's, he's an international icon. So you, it transcends markets.

Steve Kroft: So how big's the market outside the United States and outside of Milwaukee?

Peter Feigin: More than 50 percent of our digital traffic is from out of the U.S. You know, more of our video views are outside of the U.S. And it's growing.

And Giannis has a following like no other player in the NBA. Often after road games, he meets with large contingents of Greek Americans.

On a night after a game in Cleveland, an hour after a tough loss, 200 were waiting for him. He joined them in singing the Greek national anthem and hung around to take a selfie with his people. It brings back memories.

He was born in Athens in 1994 into poverty on the lowest rung of Greek society. His parents had come here from Nigeria and raised their family. They had no papers, lived in tiny two-room apartments, sleeping three or four to a bed. There was rarely enough food.

Giannis Antetokounmpo: You know, it was tough. We didn't have a lot of money. But we had a lot of happiness. So we wasn't broke happiness wise. When we were struggling back in the day, we were all together in one room, same room. We were having fun. We were smiling. There was some tough times.

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Steve Kroft: You think it made you stronger?

Giannis Antetokounmpo: Oh yeah, definitely.

They subsisted in the shadows of the economy, peddling goods on the streets, just like these African migrants, hoping to make $25 or $30. Always one step ahead of the law.

Steve Kroft: What were you selling?

Giannis Antetokounmpo: We used to sell glasses, watches. Then, we used to sell CDs, DVDs.

Steve Kroft: You must be a pretty good salesman.

Giannis Antetokounmpo: I was the best.

Steve Kroft: The best

Giannis Antetokounmpo: I was really good at it.

Steve Kroft: What was your secret?

Giannis Antetokounmpo: I didn't give up. I was like, I always keep asking them questions. And I was cute too. I was young.

Steve Kroft: You pestered them until they bought something.

Giannis Antetokounmpo: Yeah.

Steve Kroft: Are you still like that?

Giannis Antetokounmpo: Persistent in life? I think yes I am. Like, I'm gonna do something until I get it right.

It was Giannis's father who encouraged him and his older brother Thanasis to pursue basketball as a possible career. He had given them Greek first names to help them assimilate, but it was basketball that helped them fit in, and the brothers began playing on this neighborhood court. We met Thanasis in Athens where he is a member of the Greek National Team and plays in a top European league.

He took us to the tiny, dingy gym which was their home court until five years ago.

Steve Kroft: This is where you and Giannis were playing when he got drafted?

Thanasis Antetokounmpo: Yeah. This is our gym. I mean, you can see the photos up there.

The memories are still here. So are the leaky showers and the stale air in a locker room barely large enough to accommodate the starting five.

Steve Kroft: So were you two of the youngest people on the team?

Thanasis Antetokounmpo: Yeah, almost every year. Almost every year, yes.

They were both making less than $500 a month playing in the Greek second division, more than they could make hawking sunglasses but not enough to afford multiple pairs of sneakers.

Steve Kroft: What did you do for basketball shoes?

Thanasis Antetokounmpo: Depends. I remember one game we played with the same pair. One game.

Steve Kroft: You would come out of the game and you would give your shoes to him?

Thanasis Antetokounmpo: Yeah.

Then in early 2013 something weird happened. An international talent scout posted grainy video of Giannis online. He was a raw, 18-year-old beanpole averaging just nine points a game.

Steve Kroft: Were you the best player in the league?

Giannis Antetokounmpo: No. I wasn't. I wasn't. There was a lot of players better than me. But I had a lot of potential to be better than them.

One of the first to spot it was Alex Saratsis, a Chicago agent, born in Greece, who had already watched Giannis play during a trip to Athens.

Correspondent Steve Kroft and Giannis Antetokounmpo CBS News

Steve Kroft: Who was he playing against?

Alex Saratsis: It's like the equivalent of the the YMCA. I would say. You have guys who have normal jobs. Who work 9 to 5. Guys who would be smoking cigarettes before games. But that would be who he'd be playing against.

Saratsis signed Giannis up as a client, and over the next few months watched virtually every NBA team make the pilgrimage to the tiny gym in Athens to appraise what they thought might be an uncut diamond.

Alex Saratsis: You look up in the stands in the gym that holds maybe 40 people. And 20 of them are NBA people.

Steve Kroft: That's crazy.

Alex Saratsis: Yeah.

In June of 2013, he was invited to attend the NBA draft. And with a new passport in hand, Giannis and his brother boarded a plane to America.

Steve Kroft: So what was he like when he got off the plane?

Alex Saratsis: He had no idea what's going on. I asked him, I said, 'what color's your suit? And he said, 'What suit?' I said, 'The suit for the draft?' He's like 'I didn't know I needed to wear a suit.' He said, 'Where would I buy a suit?'

They managed to get one in time for Giannis to hear his name called as the 15th pick of the first round.

David Stern at Draft: The Milwaukee Bucks select Giannis Antetokounmpo.

Giannis Antetokounmpo: I was so excited. I was like you guys gotta go get my brother. Thanasis came, gave me a hug. We started crying. We just knew our life changed at that moment. From now on, our family gonna have a better future.

Steve Kroft: How'd you celebrate?

Giannis Antetokounmpo: How we celebrate, we didn't do nothing. There was a lot of other players going out to the clubs, getting drunk and stuff. Me and Thanasis just went back to the room excited.

Steve Kroft: Did you jump on the bed?

Giannis Antetokounmpo: Yeah, we started jumping on the bed too.

He was still wearing his new suit the next day when he flew to Milwaukee for his formal introduction.

Steve Kroft: Did you know anything about Milwaukee?

Giannis Antetokounmpo: At the time, no. Nothing.

Steve Kroft: Did you know where it was?

Giannis Antetokounmpo: No.

Steve Kroft: Didn't know what the weather was?

Giannis Antetokounmpo: No

Steve Kroft: Didn't know how big the arena was.

Giannis Antetokounmpo: Nothing

Steve Kroft: How good they were?

Giannis Antetokounmpo: I didn't know the players. I didn't know nothing about Milwaukee. I didn't know nothing about the NBA period

That's not all the 18-year-old didn't know. His English was sketchy, he didn't know how to drive, or use a bank account. After trying his first smoothie, he sent out a tweet.

Giannis Antetokounmpo: 'Man, I just had my first smoothie. Man, God bless America.' That's what I said. Oh man.

Giannis lived in a hotel and was alone for five months until his parents and brothers got their visas to join him. And there was the very steep learning curve of adapting to the NBA. He averaged just six points and three rebounds in his rookie year. But there were moments of brilliance like this defensive sequence that kept everyone's hopes up.

John Henson: He blocked a shot, fell, blocked another shot and I think that was probably the start of what he could become in kind of a flash of his potential.

Steve Kroft: What do you make of his progression?

John Henson: I think from the third year on, it, it went from kind of a slight slope to straight up.

This year, Antetokounmpo finished second in the All-Star balloting and first in votes cast by NBA players. Right now he is averaging 27 points and ten rebounds a game against the best competition in the world and his brilliance is now taken for granted.

Peter Feigin: We knew there was a prospect of him being very special but we didn't know it was going to be like this. The interesting thing about Giannis is there's not a game that something extraordinary doesn't happen.

Bucks President Peter Feigin and his team's marketing department seem to be making the most of it.

Peter Feigin: And the second he started holding the ball a bit more...

Steve Kroft: What's going on?

Peter Feigin: This is part of the Giannis effect.

Steve Kroft: Oh yeah?

Peter Feigin: This is called sales.

Steve Kroft: What have you just sold?

Peter Feigin: We've sold a season ticket.

Steve Kroft: How many of those do you sell?

Peter Feigin: Well, we've sold a few thousand, and we hope to sell a little bit over 10,000 before the new arena opens.

The new $500 million facility, the house that Giannis helped build, is pumping huge amounts of money into Milwaukee's economy and is supposed to be ready for next season. Giannis got a private tour in January.

In the rafters, construction workers began a chant he's hearing more often: MVP, MVP.

The kid who once had to share his sneakers with his brother will soon have his own signature shoe from Nike, the first foreign-born player to receive that tribute. In Athens, on the playground where 'The Greek Freak' made his first baskets, an artist has painted a fresco on asphalt in his honor.

And when the largest airline in his native country needed someone to symbolize the glory of Greece in its commercials, it chose a young man who had once been an outcast here.

Steve Kroft: What's it like when you go back to Greece now?

Giannis Antetokounmpo: The people go crazy now. And it's absolutely unbelievable, it's absolutely unbelievable.

Steve Kroft: You're a big deal.

Giannis Antetokounmpo: They think I'm a big deal. I don't know if I'm actually a big deal.

To date, Giannis Antetokounmpo professes no love for bright lights and big cities. He's made Milwaukee his home and he's content being a big presence in a small city.

Giannis Antetokounmpo: I think for a guy like me, low-profile guy, it's better being in Milwaukee.

Steve Kroft: You think you're low profile?

Giannis Antetokounmpo: Yeah.

Steve Kroft: You wanna be low profile?

Giannis Antetokounmpo: Always

He'll make $22 million this year, yet he lives in a two-bedroom rental apartment with his mother, his girlfriend and his youngest brother. When he's not on the road, he is usually in the Bucks practice facility working on his jump shot or just working out.

As he said earlier, he likes to do something until he gets it right.

Steve Kroft: How good do you think you can be? You think you're gonna keep getting better?

Giannis Antetokounmpo: Oh yeah. Yeah. I have to. There's not a choice.

Steve Kroft: What do you mean?

Giannis Antetokounmpo: I'm really scared of failing. So I gotta get better.

For the rest of the NBA, the idea 'The Greek Freak' might even get better is a very scary thought.

Produced by Draggan Mihailovich. Associate producer, Laura Dodd.