Seattle also waived left-hander pitcher Ryan Borucki and right-hander Casey Sadler, leaving its 40-man roster at 36.
The 27-year-old Speier made 17 appearance last season for the Royals and was 0-1 with a 2.33 ERA. He appeared in 41 games over parts of four seasons all with Kansas City.
The 24-year-old McGee spent his entire baseball career in the Tampa Bay organization after being a fourth-round pick by the Rays in 2016. He has appeared in one major league game, coming in October when he pitched three innings, allowing one unearned run. McGee was designated for assignment by the Rays on Oct. 3 and claimed by Boston two days later.
Borucki appeared in 21 games last season for Seattle, but none after early August due to left flexor strain. He was 2-0 with a 4.26 ERA during his time with the Mariners. Borucki was acquired from Toronto in June.
Sadler missed all of last season due to a labrum injury in his right shoulder. The 31-year-old appeared in 42 games for Seattle in 2021 and allowed three earned runs in 40 1/3 innings pitched.
AP MLB: https://apnews.com/hub/mlb and https://twitter.com/AP_Sports
The Associated Press