Williams (elbow) threw a simulated game at Nationals Park ahead of Tuesday's loss to the Marlins, MLB.com reports.
The veteran right-hander still lacks a concrete timeline for his return from last July's internal brace procedure on his elbow, but Williams is making progress in his recovery. He'll need a lengthy rehab assignment, but he could be a month or so away from providing the Nationals' beleaguered staff with an additional rotation option.