The Buffalo Bills relinquished their exclusive negotiating rights with guard Andy Levitre on Friday. Meanwhile, it remained to be seen whether the Bills would demand a restructuring of the contract of quarterback Ryan Fitzpatrick as the NFL prepared for the start of the free-agent shopping season. Levitre is the Bills’ top fully unrestricted free agent, and he became free to negotiate with other teams early this morning – as soon as the clock struck midnight – under a new NFL rule. The NFL’s free-agent signing period does not begin until 4 p.m. Tuesday. But this year there is a formal three-day period before the start of the new league year in which teams can negotiate with the agents of all players set to become free agents. The Bills had no deal with Levitre as of Friday, a sign they are being prudent with their offensive line budgeting. Tackles are a higher priority than guards in both the draft and free agency. Many teams want to be careful about how much money they devote to their interior offensive linemen.