Guerra was recalled from Triple-A Rochester on Tuesday, Dan Kolko of MASN Sports reports.
Guerra has spent time in the big leagues across 10 previous seasons, but this will mark the veteran right-hander's first trip to the majors in 2021. Guerra most recently posted a 4.02 ERA across 15.2 innings with Washington during the shortened 2020 campaign. With former closer Brad Hand having been dealt to Toronto and the Nationals dealing with injuries in their bullpen, the possibility of Guerra receiving some high-leverage innings isn't out of the question.