The team did not disclose terms of Manalac's deal on Saturday.
• Sunday: Colts at Bills, 1 p.m. ET (CBS)
The 6-foot, 235-pound Cincinnati product was signed to Buffalo's practice squad on Dec. 23. He was in training camp with the Bills as an undrafted free agent but was released before the start of the regular season.
Johnson, a seven-year veteran who has also played for the Chicago Bears and St. Louis Rams, appeared in eight games this season for the Bills.