Whilst Rodgers insists he does not want to lose the Denmark defender, he also recognises City have the cash to lure any player.
But, ahead of Thursday night's Europa League qualifier with FC Gomel at Anfield, Rodgers indicated Roberto Mancini will have to dig deep.
"Thiago Silva has left AC Milan for PSG for £40million. He [Agger] is one of the leading players in European football, so it is going to be a big valuation.
"Is he a player I want to lose? No. He understands how I want to work and can play a real pivotal part in how I want to play.
"But I am a realist. If someone comes in with a massive bid and it is in the best interests of the club, whether it is Daniel or any other player, you have to look at it."
Rodgers's words underline the brutal reality of life at Liverpool.
The club are heading towards a third successive season outside the Champions League, a tournament they won as recently as 2005 and owner John Henry has made it clear he simply will not fund the kind of massive signings splashed out on during Kenny Dalglish's ill-fated 18 months in charge.