Luke Freeman was absent from Bristol City's defeat to Cardiff on Saturday as a move to Championship rivals QPR nears ever closer.
Speaking to the Bristol Evening Post, Johnson had this to say: "
"We still live in hope that he will sign that contract, but we cannot wait forever. We're keen for Luke to stay, but it remains unresolved.
"January can be a destabilising time for clubs, because it's a time when agents make their money. They'll do anything to achieve that and it doesn't help."
Johnson added: "The objective is for Luke to stay, but there always comes a tipping point and the owner has made it very clear what the boundaries are in terms of the contract and the fee if we decide we want to move him on."
City are likely to leave Freeman out of their match day squad until his future is resolved but the player himself must decide whether to move on now or sign a pre-contract agreement to make the switch in the summer.
Ultimately, City fans will want Freeman to stay but his indecision indicates his mind is already elsewhere.
Ian Holloway's side are looking to fill the void left by Tjaronn Cherry and the acquisition of Freeman could prove paramount.
Freeman has gone on to make over 180 appearances in the football league since making his debut for Gillingham in 2007 scoring 24 goals.