A piece from Julian De Martinis when asked if Marco will go to Barca:
"Well, first of all, I want to preface this by saying what I did in a different thread: Roma have no reason to sell him. He's on year one of a four or five year deal (I forget at the moment; believe it was 4 year initially but Roma are on the verge of giving him a raise and an additional year), and the club's project means that Marquinhos, Pjanic, and Destro are the building blocks. The whole point of what Sabatini did the past two years was to find talents like those three; to sell them means we're the next Udinese, while the management has made it very clear that they want us to be the next Barcelona.
So, all that being said, let's still say hypothetically he moves to Barca. You have to understand one thing: he's 18. This is his first season playing in Europe and he's only played 20 Serie A games. Ever. He's never played in a European competition; never in a match where a trophy was on the line. Roma this season has been an ideal setting: there's massive pressure, to be sure, but no trophies on the line.
In short, I can't say for sure he isn't a one-season wonder, or that he'll flop whenever trophies are on the line.
I can say that, from what I've seen, which is every match he's played in, he looks far, far more likely to me to become a widely known and respected world-class CB than anything else. His positioning is usually phenomenal; he reads the game better than almost any other defender we've had since Juan was great; he knows when to tackle, when to chase, and how to use his athleticism in the rare cases that someone does get past him. He's bailed out our defense more times than I can count in those 20 games.
Will he stay like that forever? Will he still be that good next season? I suspect yes, but the sample size is really small right now. I think moving to Barca this summer would be a massive mistake after merely one year in Europe; the jump to a club that's consistently in the hunt for a treble is just too high, and I think many players ruin their careers and stunt their growth by moving to big sides where they just rot on the bench.
I mean, look at Nuri Sahin; was his Madrid move really worth it? He's back where he started now with a year less of starting football. More money is always nice but so is always playing (I know Barca need CBs, so this might not apply exactly to Marquinhos, but the jist is the same: big clubs come with a lot more responsibility and squad rotation in general)."