The defender helped the Tigers win promotion to the Premier League but was loaned to Nottingham Forest this season, and Steve Bruce has now urged action from the Championship side
The 25-year-old captained the Yorkshire club to promotion from the Championship last season, but was loaned to Nottingham Forest - who are also thought to be keen on signing him permanently.
And Bruce has confirmed he would be happy to see the former Liverpool man leave the KC Stadium in January - warning Forest they will have to move fast if they want to compete with Reading's offer.
"The way it stands is we've have a substantial offer from Reading," Bruce told the BBC. "Ultimately it's always in Jack's hands, but Nottingham Forest have to come to the table and play ball with us.
"We will be calling Jack and the ball is now in Nottingham Forest's court. He is available, we've said that to everybody and we'll see what happens.
"My job is to look after the interests of the club and if somebody is offering us a lot of money then we have to look at it, it's as simple as that.
"We obviously let him go on loan as there were doubts about his knee and we understand that.
"He has gone there and done very well, but if they think they are going to get him for nothing, then we've got a decision to make."
Hobbs has made 27 appearances for Forest this season, scoring his only goal in September's 1-0 win over local rivals Derby County.