Merriman said Friday he didn't think the injury was significant. The Bills will have their bye next week, giving him an additional week to heal.
The seven-year veteran has a history of problems with his right tendon, but the team has not indicated which Achilles' Merriman injured this time. He aggravated the injury during his first practice with the Bills in November of last season after the team claimed him off waivers from the San Diego Chargers.
Merriman finished last season on injured reserve.
With both Merriman and Chris Kelsay (calf) out, the Bills will be down to two healthy outside linebackers -- Danny Batten and Arthur Moats. Defensive lineman Spencer Johnson will also be available to fill in after working with the outside linebackers on Friday.
The Associated Press contributed to this report.