Williams names Jordan Zimmermann the No. 2 starter, followed by Stephen Strasburg, Gio Gonzalez and Doug Fister.
The right-hander said his right bicep feels better and expects to start on Tuesday.
The right-hander is resting his strained right bicep and could throw for the first time during Thursday's team workout.
Based on performance, the 2014 rotation and 2012 rotation may be the best in Nationals history.
The left-handed reliever will be with the Nationals for, at least, the weekend as an extra arm in the bullpen.
As the Nationals prepare for the return of Doug Fister, their Tuesday starter remains up in the air.
Gio Gonzalez, Jordan Zimmermann and Stephen Strasburg will face the Miami Marlins.
Both Tanner Roark and Taylor Jordan will pitch Saturday at Nationals Park, and the Nationals will announce their fifth starter afterward.
In a minor league game, Tanner Roark helped his cause in the competition for the Nationals' final rotation spot.
Ross Detwiler will start the year in the bullpen, leaving Tanner Roark, Taylor Jordan and perhaps Chris Young fighting for the final rotation spot.