The Guardians declined their side of Armstrong's $8 million mutual option for the 2027 season Friday, Tim Stebbins of MLB.com reports.
Armstrong appeared in 41 games for Cleveland this year, turning in a 4.58 ERA and 1.39 WHIP with a 34:19 K:BB across 35.1 innings. The Guardians didn't deem his performance worthy of bringing him back for $8 million, so they will instead pay him a $1.5 million buyout and let him enter the open market.