Ryan Seymour was standing on the visitor’s side of Candlestick Park on Sunday.
Two days later, he found himself sharing a locker room with the opponent.
The 49ers announced Tuesday they signed Seymour from the rival Seattle Seahawks’ practice squad to a three-year contract as insurance at the left guard position.
Starter Mike Iupati has missed the past three games with a sprained left knee and left tackle Joe Staley returned for Sunday’s win against the Seahawks a week after spraining his right knee.
The 49ers (9-4) placed defensive tackle Tank Carradine, the teams’ second-round pick in April, on injured reserve and signed wide receiver Devon Wylie to the practice squad.