Quackenbush has been named to the Nationals' 60-man player pool, Jessica Camerato of MLB.com reports.
The 31-year-old signed a minor-league deal with the Nats in January, but his big-league experience has earned him a look as an emergency bullpen option for the club this season. Quackenbush hasn't had much success since 2016, however, posting an 8.66 ERA, 1.90 WHIP and 30:22 K:BB over his last 35.1 MLB innings.