The Bluebirds have managed to retain the core of their squad so far, but the transfer window remains open until August 31.
With that in mind, the Welsh outfit have a few nervous weeks to negotiate before they can relax and focus their full attention on matters on the field.
The likes of Ross McCormack and Joe Ledley continue to be linked with moves to the top-flight, with the duo reported to be on the wish lists of numerous clubs.
Marshall accepts that big-money bids could yet be tabled for Cardiff's key men, but the Scottish keeper believes the club are capable of spurning such advances.
"There are only a couple of weeks to go until the transfer window closes so hopefully the club can get past that stage without selling someone like Joe Ledley," he said.
"It puts a smile on my face when I see the likes of Newcastle and Middlesbrough selling their stars because they have good Premier League players and it makes our job that bit easier."