Paxton has been diagnosed with a Grade 1 hamstring strain and will be shut down from throwing, Pete Abraham of The Boston Globe reports.

EDGE Analysis

The veteran southpaw left his start Friday with discomfort. While Grade 1 is the least severe classification of strain, it will likely delay Paxton's start to the season. With Brayan Bello (forearm) and Garrett Whitlock (hip) also unlikely for Opening Day, the Red Sox may need to roll with Tanner Houck and/or Josh Winckowski in the starting rotation.