The former Preston goalkeeper has been immense at Hillsborough over the past three years but officially rejected a contract extension in writing over the weekend.
Lucas still is recovering from a knee injury and it is expected he will be out of action for some considerable time but he will still stay at Hillsborough to use the club's facilities.
Now Sturrock needs a new goalkeeper with Chris Adamson being left as the club's only senior stopper - although he is still pursuing the option of getting England squad member Scott Carson on a season-long loan.
Sturrock told the club's official site: "I will talk to Liverpool (about Carson) over the next couple of days to find out the situation and I hope they can mark my card either way.
"But I haven't left all my eggs in one basket and I will be working to bring a keeper in soon - hopefully by June 26."