Nathan Eovaldi takes his place.
https://www.espn.com/mlb/story/_/id/31140302/eduardo-rodriguez-scratched-opening-day-dead-arm-nate-eovaldi-start-opener-boston-red-sox
The only hopeful bit of news concerning this: "Cora clarified that Rodriguez could avoid a stint on the Injured List and that the missing start is unrelated to the myocarditis that led to the 27-year old missing the 2020 season."
https://www.espn.com/mlb/story/_/id/31140302/eduardo-rodriguez-scratched-opening-day-dead-arm-nate-eovaldi-start-opener-boston-red-sox
The only hopeful bit of news concerning this: "Cora clarified that Rodriguez could avoid a stint on the Injured List and that the missing start is unrelated to the myocarditis that led to the 27-year old missing the 2020 season."