Unstoppable: Barcelona’s Lionel Messi leaves opposing players in his wake during a recent La Liga game. (AP Photos).

Imagine it’s 1958 and you just watched a 17-year-old Pele burst upon the global soccer scene.

Or it’s 1968 and you get to see George Best and Manchester United win the European Cup over Benfica.

Well, Saturday could be one of those unforgettable moments in time even if it is an exhibition rather than a competitive game.

The player to watch when the U.S. plays Argentina live at 4 p.m. on ESPN2 is not (with all due respect to Bob Bradley’s boys) the likes of Jermaine Jones.

No, we have a rare chance to see one of the greatest soccer players ever at the height of his powers, who is perhaps having the defining season of an already brilliant career – Lionel Messi.

Associated Press Sports Writer Ronald Blum explains:

NEW YORK (AP) — Most of the 80,000 fans in Camp Nou rose to their feet, again astonished by what they had just witnessed.

The slow singsong reverberated around the steep, smoke-filled stands of Europe’s largest stadium on this November night, getting louder and louder with each chorus.

Many raised both arms and repeatedly took deep bows in homage.

“Messsss-iiiiii! Messsss-iiiiii!” they chanted over and over.

Lionel Messi ran to the edge of the stands, cupped his left hand to his ear and raised his right quickly a few times, urging the spectators to let him hear the noise. After his
teammates mobbed him, he walked back toward the center stripe, and pointed the index fingers of each hand to the sky, in tribute to his grandmother. He raised both outstretched arms to shoulder level a few times, causing the singing to get more intense.

This scene at the match against Villarreal is repeated in Barcelona week after week, goal after goal after goal after goal, at a rate not seen in more than 60 years.

Far from his adoring fans in Catalonia, the world’s greatest player comes to the United States on Saturday night to lead Argentina in an exhibition against the American national team at the Meadowlands — a few hundred feet from the old stadium where Pele once played. If Messi keeps it up for a few more years, he will end the debate over whether Pele or Maradona is soccer’s greatest player ever. Messi will raise himself above both.

“His ball control is perfect. And his vision is just something else. It seems like he can kind
of see 360 degrees,” former German great Juergen Klinsmann said. “He has that God-given talent that he knows exactly where the goal is, no matter how is he positioned.”

At 23, he already is a two-time FIFA player of the year, a member of two Champions League winners. He has 173 goals in 256 games for Barcelona since making his competitive debut in 2004. He has 16 goals in 54 appearances for Argentina.

Still, don’t proclaim Messi the best around Pele — not just yet.

“Since I started my career, after 1958 when Brazil won the World Cup, every time they have someone to compare to Pele,” the Brazilian great said last month. “The first one was Puskas, then Di Stefano, then Platini, then Maradona, then Beckenbauer, then Francescoli, then Zico.

But no doubt Messi today is one of the best players. He’s skillful and he deserves to be the best player at the moment.”

Having won the FIFA player of the year award in 2009 and 2010 — joining Brazil’s Ronaldo and Ronaldinho as the only back-to-back winners — Messi has put together an even better season.

With 45 goals in 42 games for Barcelona, he has the Blaugrana on course for a third straight La Liga title for the first time since the Dream Team won four in a row from 1991-94.

Barcelona has a five-point lead over second-place Real Madrid with nine league games left, is in the Copa del Rey final on April 20 and reached the quarterfinals of the Champions League, which the club won in 2006 and 2009.

Messi’s first goal against Arsenal on March 8, in which he flicked up and over onrushing
goalkeeper Manuel Almunia before volleying the ball into the net, had Barcelona faithful
discussing whether it was his best ever. The consensus was while it was among the top 10, the best came against Getafe in April 2007 in which he picked up the ball in his own half, accelerated past four defenders and rounded the goalkeeper — similar to Diego Maradona’s score against England in the 1986 World Cup.

“To talk about if it’s one of Messi’s best goals, there’s no point,” Barcelona coach Pep
Guardiola said after the Arsenal game. “He scores such great goals they become normal.”

And that wasn’t even Messi’s best game against the Gunners. Last April 6 in the quarterfinals, he became only the sixth player to score four goals in a Champions League game.

“He’s a PlayStation,” Arsenal manager Arsene Wenger said that night. “For me, he is the best player in the world — and by a distance. Once he’s on the run with the ball, he’s unstoppable. He’s the only player who can change direction at such a pace.”

With Barcelona, he’s surrounded by many of the world’s top players. Xavi Hernandez and Andres Iniesta are the Scylla and Charybdis of the Barcelona midfield, obstacles opponents rarely canget the ball past.

But even Messi’s heralded teammates are amazed by what they see each match.

“It’s hard to explain about Messi. What he is doing isn’t normal but we’re all starting to see it as something regular,” Javier Mascherano said. “He’s making history, and let’s hope hecontinues to do so for many years for us and for everyone.”

Messi has had less success with Argentina, eliminated by Germany in the World Cup
quarterfinals in both 2006 and last year. While he led his nation to titles at the 2005 FIFAWorld Youth Championship (for players under 20) and the 2008 Olympics, he hasn’t won any championships with the senior national team. The Copa America in July is especially important because Argentina is the host.

“He’s done OK for Argentina, but he hasn’t taken the world apart like he’s taken Europe apart with his club side,” Sky Sports broadcaster Martin Tyler said. “I think if you’re an attacking player you’re dependent on the strength of the side around you, and he’s perfectly placed. (Barcelona’s) passing game is just perfect for him. He’s got so many players on his wavelength. He’s sublime. It’s as good as you could wish to see.”

Messi left the youth program of Newell’s Old Boys, his hometown team in Rosario, and arrived at Barcelona in September 2000 at the age of 13 because the club agreed to pay for treatment for his growth hormone deficiency. He was 16 when he made his first appearance for the senior team in an exhibition against Porto in November 2003, and made his league debut the following October against Espanyol. He was 17 when he scored his first competitive goal for Barca, against Albacete in May 2005.

His left foot is lethal — 135 goals for Barcelona have come off his favored foot, with 29 from the right, seven on headers, one off his chest and one off a hand. He trails only Cesar Rodriguez (235), Laszlo Kubala (196) and Josep Samitier (178) on the club career scoring list. With up to 15 games left this season, he has an outside chance to reach the European record of 66 goals in a club season, set by Ferenc Deak for Hungary’s Ferencvaros in 1948-49.

At 5 foot-5, Messi is proof that size isn’t the determining factor in soccer that it can be
in other sports.

“The fact that he’s built very slight — I mean his nickname’s The Flea, isn’t’ it? — that
helps him because he doesn’t seem to get injured, which is an art form in itself,” said former Liverpool and Real Madrid star Steve McManaman, now an analyst for ESPN. “Every time he gets kicked, he just bounces up off people, gets up and carries on, doesn’t he? His temperament, as well, for the game I think is astonishing.”

American defenders expect a difficult night. Messi hasn’t scored in two games against the U.S., although he did have the assist for the first goal when the teams met at the 2007 Copa America.

“He’s the best player in the world, so it’s always a wonderful challenge to put yourself
against those types of players,” central defender Jay DeMerit said. “He’s as fast with the
ball as he is without it. He always seems to be a step ahead.”

The New Meadowlands Stadium will be sold out or close to it on a cool early spring night, with Messi the reason many bought tickets for an interesting but meaningless match.

“I can’t think of a negative to say about him, with the possible exception that he hasn’t yet taken Argentina to win the World Cup like Maradona did,” Tyler said. “And that’s only an achievement, it’s not a negative of character. He just picks himself up. He gets kicked. Yet somebody comes again. He doesn’t get disheartened. He’s not a prima donna.

“On this planet, at this time, he’s the greatest.”