Both Lions president Tom Lewand and general manager Martin Mayhew have said recently a successful free agent shopping spree was not predicated on the team working out a contract extension with quarterback Matthew Stafford. "Matthew Stafford is our quarterback and we hope he's our quarterback for a long time, and the reason to explore an extension is to fulfill that goal," Lewand said last month. "It's not a short-term look at the salary cap. That's the wrong way to look at that." Perhaps, but without getting some cap relief, the Lions will be hard-pressed to re-sign their own free agents, let alone bid on players like running back Reggie Bush or safety Glover Quin. At present, without knowing the exact amount of DeAndre Levy's new deal, the Lions are approximately $5 million under the cap with the free agent period officially starting at 4 p.m. Tuesday. By working an extension with Stafford, whose cap hit for 2013 is $20.8 million, they could drop another $10 million or more. But, by all accounts, it won't be a slam dunk. "It's never easy," said Mayhew, who commenced negotiations with Stafford's agent Tom Condon during the combine. "It's going to be a challenge. It's always a challenge for good players. The easy ones are with the players who aren't that good." The reason it will be particularly difficult in this case is Stafford has all the leverage. He will make in excess of $20 million this season and $19.3 in 2014. Even if the Lions were to slap the franchise tag on him after that, which they could, he would be paid more than $23 million for 2015. "Peyton Manning always played his contracts out," NFL Network reporter Albert Breer said. "The Colts restructured his deal so many times, the back end of his contract rose and rose and rose and he would have an enormous franchise tag at the end. From The Detroit News: