"He has experience there. He's done it before," Williams said of Strasburg, according to The Washington Post. "And he's earned it."
The Nationals open the season March 31 at Citi Field against the New York Mets.
"We spoke to Jordan," Williams said. "He's good with wherever and whenever he pitches. Opening Day is important. But the rest of the games are important, too."
Williams said he has been impressed by Strasburg's work ethic this spring, particularly when it comes to improving his game.
According to The Post, the left-handed Gio Gonzalez will follow in the rotation as the No. 2 to split two right-handers in Strasburg and Zimmermann. The remaining spots will be determined later in spring training.
Doug Fister is set to be the fourth starter if he can get ready in time after being sidelined by elbow inflammation.
Information from The Associated Press was used in this report.