Brazil captain Silva picked up his second yellow card of the tournament on Friday during the team's quarter-final win over Colombia.
While Neymar's tournament-ending back injury has been the focus of discussion, ex-England international Ferdinand believes that Silva's absence could be more damaging to the host nation's hopes of reaching the final.
He tweeted: "Thiago silva missing the next game is arguably more worrying for Brazil than Neymar missing it. Best defender & leader. Willian & Dante in?"
Brazil and Germany play their World Cup semi-final in Belo Horizonte on Tuesday evening.