Sergio Agüero is following in Robin van Persie's footsteps, and that's bad

He was an Argentine wunderkind, debuting in the first division a month after his 15th birthday and scoring 18 goals in a season before his 18th birthday. He twice won the U-20 World Cup, once leading it in scoring, and was named FIFA's Young Player of the Year. By the time he was 18, he was playing for the senior team and by 19, he had scored 27 goals for Atletico Madrid.

Sergio Agüero was supposed to be a superstar by now. He was supposed to be one of the best strikers in the world. Any conversation that includes Radamel Falcao, Zlatan Ibrahimovic, Edinson Cavani or Luis Suarez is supposed to include him. But that's not the case.

Instead, Agüero heads into Argentina's World Cup semifinal against the Netherlands on the verge of becoming like the man he will be facing -- Robin van Persie.

The reason Agüero's rarely considered one of the world's finest has nothing to do with his ability. Instead, it's because he can't stay on the pitch. Even when he's healthy for an extended period, he's dogged by questions about when he'll next get hurt. If he can't change that soon, he'll never be able to do it. And soon may have to be on Wednesday, while van Persie stares at him as a reminder of the hole he's so close to falling in.

Nobody doubts the Argentine's quality, just his availability. A bad hamstring, or knee, or groin, or really anything, has kept the 26-year-old off the pitch and on the training table for large chunks far too often in recent years and because of it, discussions that used to be about how brilliant he is have turned to discussions about what could have been.

Sure, Agüero scored six goals in six group stage matches last Champions League, but he managed just 45 minutes in the knockout stages due to injury. What if he was fit? And yeah, Agüero was fourth in the Premier League in goals last season, but he only started 20 league matches. What if he was fit enough to start 33 like Luis Suarez?

The question of "what if" has dogged Agüero into this World Cup too. Argentina's attack looked potent in the group stages, but they've managed just one goal in both of their knockout stages matches, and Agüero has played in neither. While Lionel Messi dazzles, dribbling around defenders and feeding teammates with sublime passes, he's seen his work wasted more often than not. What if Agüero had been fit enough to lend Messi a helping hand?

It's a conversation van Persie knows all too well.

The Dutch striker was awarded the KNVB Best Young Talent Award at 19 years old and named Dutch Football Talent of the Year 12 months later. He led Arsenal in scoring four times and led the Premier League in scoring twice, while also earning the Bronze Boot at Euro 2008. But like Agüero, he's not in the conversation as one of the world's best strikers. Or at least, like Agüero, he's in the conversation but he's never the conclusion.

Even after being the Premier League's top scorer in consecutive seasons and securing a move to Manchester United, van Persie was dogged by questions about whether he could stay fit. Sure, he scored 56 goals in two seasons, but he also did it in the only two seasons he ever remained fit. What would happen if he got hurt again?

Unfortunately, that's what happened. Van Persie was limited to 21 league matches last season and even carried a knock into this World Cup. No matter how good van Persie is and how many goals he scores, the Dutchman will never get past his injuries. It will always be a part of the conversation, keeping him from the upper echelon of strikers. As soon as his name comes up in a discussion that includes Falcao, Ibrahimovic and the rest, he's relegated down to 'could have been' on account of his checkered injury past. And at 29 years old, that's never going to change.

Agüero hasn't been relegated to van Persie's category in perpetuity. Yet.

Agüero can still be the player everyone expected him to be at 15. And 17. And 19. And even at 24, when he was a 30-goal scorer for the Premier League champions. That was only two years ago, as ancient as it feels, but that is the product of the changed conversation -- one that is as much about his time on the sidelines as his time on the field.

After two matches on the training table, Agüero is set to return. He'll do it in the World Cup semifinals on his home continent. And he'll do it by pulling on Argentina's blue and white and looking across the pitch at van Persie.

He can score a goal and be the help Messi so desperately needs. He can put Argentina in the final and bring home the World Cup title his country has been waiting 28 years for. It can be the start of a revival for Agüero, one that continues at City and marks the resumption of his climb to the highest of heights.

If Agüero is going to be one of the best of the best, it starts against Netherlands -- against the man he so desperately needs to separate himself from.