Indeed. Barcelona offered to pay his medical bills for his growth problems, it meant that Messi had to move to Barcelona but what a great gesture. Messi would never have made it otherwise, because no team in Argentina could afford his medical fees. He did have injury problems at Barcelona but that was due to the treatments he was getting, in fact I think they sacked the doctor who was responsible because of it. Since then he has very very rarely missed a match.
It's funny like you say how some of the world's best players are small (Xavi, Iniesta, Messi, Scholes) but the talent can be spotted much earlier.