Calenda told Mundo Deportivo: "The club told us he could leave. There are offers from PSG, Manchester United and Barcelona."
Marquinhos, a young but stunningly-talented centre-back, excelled in an otherwise-dodgy Roma defence in the Serie A last season. He is freakishly good for his age, so much so that he has a genuinely eerie quality to his talent, in the manner of a true prodigy. It's not bombastic at all to claim that he could be the best in the world, and is probably on a level that, in his age group, includes only Raphael Varane at present.
He'd probably cost a fair amount, but if we're going to buy a centre-back, this is a much more exciting option than Ezequiel Garay or Davide Astori. The source isn't the most reliable - agents link their players to clubs all the time for a host of reasons - but United's interest has been mooted before and the player is probably leaving in this window.