Solis was optioned to Triple-A Syracuse on Thursday, Mark Zuckerman of MASNsports.com reports.
The left-hander occupied an important spot of late in the Nats' bullpen by default, considering how injury-prone and weak it has been. Solis looked out of place, considering his 14.73 ERA in 7.1 innings. The 28-year-old will now wait at Triple-A for his next ride on the shuttle. In the meantime, the Nats will make a corresponding move before Friday's second-half opener.