Perez, a left-hander, tested positive for COVID-19 earlier on Monday, Red Sox manager Alex Cora said before his team's 6-1 loss to the Tampa Bay Rays. The Red Sox went through the MLB coronavirus protocols that include contact tracing and testing prior to the series opener, which later led to the Barnes result.
Hernandez and Arroyo tested positive late last week and were placed on the list on Friday. Cora said Hernandez and Arroyo are both feeling OK.
Perez is 7-8 with a 4.88 ERA in 31 games this season, including 22 starts. Barnes has 24 saves to go along with a 6-5 record in 54 appearances.
The Red Sox, who struggled most of August, won three of four heading into the series vs. the first-place Rays. But Boston now sits nine games behind Tampa Bay in the American League East, though it remains in the AL's second wild-card position.
The Associated Press contributed to this report.