Boston left-hander James Paxton strained his right calf after five pitches of his start Sunday against the visiting Houston Astros, the Red Sox announced.
Paxton limped off the field after moving to cover first base on Yordan Alvarez’s grounder to first baseman Dominic Smith with two outs in the opening inning. Alvarez beat Smith to the bag for an infield single.
Boston manager Alex Cora and a trainer visited Paxton, who limped to the dugout with the aid of the trainer. Right-hander Lucas Sims replaced Paxton.
Boston traded for Paxton, who played for the Red Sox in 2023, on July 26 in exchange for minor league infielder Moises Bolivar. Overall, he is 9-3 with a 4.40 ERA in 21 starts this season.
Paxton, 35, is a career 73-41 with a 3.77 ERA in 177 starts for the Seattle Mariners (2013-18, 2021), New York Yankees (2019-20), Red Sox (2023, 2024) and Dodgers.