The 23-year-old, who starred in Monday's 1-1 draw with Norwich, is out of contract at the end of the season and the Teessiders know they may have to cash in on him during the winter transfer window.
Asked if any deal is close, Mowbray told the club's official website: "I don't think so, I don't think the momentum of phone calls is intense enough yet.
"Everyone is looking and maybe thinking the money might come down the more weeks we go into the transfer window.
"But from my point of view, if he's still at Middlesbrough in February, then so be it. It's important we don't let our big assets go for less than the right price.
"Wheater was immense against Norwich and to replace him would be a huge job."
Source: PA
Source: PA