Detroit Lions general manager Martin Mayhew said he had a “productive” conversation Thursday with Tom Condon, the agent for Matthew Stafford, but that talks on a new deal for the quarterback are still in the preliminary stages. “We discussed some things with Tom, and he’ll discuss them with Matthew, and we’ll follow up and have a second conversation,” Mayhew told Lions beat writers this morning at the NFL combine. “Sometimes those things move along quickly, and sometimes they take a longer time. We’re prepared for either way it goes, whether it’s a longer discussion or whether it’s a shorter discussion.” The Lions hope to sign Stafford to long-term extension both to assure his future in Detroit and free up salary cap room before the start of free agency. Stafford is set to count almost $21 million against next year’s salary cap, meaning the Lions are in a similar situation to last year, when they gave wide receiver Calvin Johnson an extension to lower his cap figure of $21.1 million. Mayhew, who was joined at the meeting by Lions president Tom Lewand and senior personnel executive Brian Xanders, said it’s not imperative that the Lions get a new deal in place with Stafford before free agency opens March 12. The Lions plan to meet this afternoon with Brian Mackler, the agent for defensive end Cliff Avril, and Mayhew said the team has identified nine of its 23 unrestricted free agents as priorities to re-sign.