Harper gave the Nationals a brief scare when he slipped on the gravel in foul territory in right field.
Zimmerman said his shoulder/upper back has improved and hopes to rest only a few days.
Williams names Jordan Zimmermann the No. 2 starter, followed by Stephen Strasburg, Gio Gonzalez and Doug Fister.
Stephen Strasburg makes his first start since twisting his left ankle.
Zimmerman left after he banged the side of his body, Storen fired a scoreless inning and Jordan Zimmermann tossed six scoreless.
Minor notes on Jayson Werth, Denard Span, Anthony Rendon and Blake Treinen.
Bryce Harper is back in the lineup after dealing with a stomach bug.
The Nationals and Astros continue to make progress toward a new spring training facility, and seem on track for the approvals they need to begin construction in the coming months.
He has pitched two innings, come in mid-inning and tossed only one inning -- a wide range of relief options.
Werth has yet to hit in a game this spring. He has been playing defense only in minor league games.