Valencia's financial problems are such that they must consider bids for anyone.
But the 29-year-old centre-half is one of the players they hope to cling on to.
Marchena is keen to discuss a new contract but, with two years remaining and a difficult summer ahead, Valencia are reluctant to spend more cash than necessary.
But the La Liga club won't be pushed into opening contract talks unless a concrete offer is made.
Marchena is Valencia's captain and was part of the Spain squad at the Confederations Cup in South Africa this summer.