The bad news was the release of linebacker Larry Foote, one of only six members of last year's team to have been a part of all three recent Super Bowls.
The day began with the re-signing of unrestricted free agent Will Allen to a one-year contract.
Allen replaced an injured Shamarko Thomas in the Steelers' quarters package last November and held the spot for the final seven games.
The Steelers then announced the two-year extensions for Miller and Polamalu, who were entering the final years of existing contracts.
Miller's new three-year deal totals $14 million with a $5 million signing bonus. The extension saved the Steelers $3.33 million against this year's cap.
Polamalu saved $4.5 million with his new three-year deal for $20 million.
Polamalu turns 33 in April and Miller turns 32 in October. Neither player received any new monies for this season in helping the team.
The release of Levi Brown, who was acquired last season but who didn't play because of an injury, saved the Steelers $6.25 million. Both he and Curtis Brown were released with the notation of "failed physical."
The release of Foote, who tore a biceps in the opener and missed the rest of the season, saved the team $1.17 million.
Unofficially, the Steelers are at the $133 million cap limit set for 4 p.m. March 11.
To make room for future signings, the Steelers still have several options, such as reaching an agreement with Jason Worilds on a multi-year contract, extending the contract of Ben Roethlisberger, restructuring the contracts of Antonio Brown and Lawrence Timmons, and asking Ike Taylor to accept a pay cut on his $7 million salary for this season.