Harper, who missed 57 games because of a torn ligament in his left thumb, was batting sixth and playing left field as the Nationals opened a series against the Colorado Rockies on Bryce Harper bobblehead night.
That meant Ryan Zimmerman, who's been playing left since being activated from his own stay on the DL, was back at third base. Anthony Rendon shifted from third to second, and Danny Espinosa was on the bench.
Asked about Zimmerman, Harper said: ''He's great. I think he should be playing left.''
''I mean, Rendon is a great third baseman, he should be playing third and we've got one of the best second baseman in the league in Danny Espinosa,'' he said. ''Of course, you want the best-hitting lineup in there and I think Rendon playing third and Zim playing left is something that's good for this team and I think that should be what's happening.''
That would presumably put Harper back in center - where he played the majority of his games during his NL rookie of the year season in 2012 - in place of Denard Span.
Williams was glad to get Harper in the lineup. As for Harper's lineup opinions, Williams didn't say much.
''I think that I would say we're happy to have him back,'' Williams said. ''And when he's out there, regardless of where he's at, we'd like him to catch it when it's hit to him and hit it when it's thrown to him. And play the way Bryce plays. That's important for us. I don't have any comment other than that.''
Williams repeated his past thoughts about moving players around depending on matchups and the need to ensure proper rest for his regulars, including 35-year-old right fielder Jayson Werth and 34-year-old first baseman Adam LaRoche.
''It's fluid,'' Williams said. ''It's today's lineup and that's going to be today's. Tomorrow's may change.''
Monday night marked the first time since opening day - when catcher Wilson Ramos left the game with an injury - that this starting eight has taken the field.
The 21-year-old Harper was hitting .289 with one home run and nine RBIs in 22 games before getting hurt. He played five rehabilitation games in the minors and hit .643, including three homers in a Double-A game over the weekend.
''To be able to get back out there and play for a team that's in contention, it's a lot of fun and I'm excited to be back,'' he said.
Washington began the day in second place in the NL East, a half-game behind Atlanta.
To make room for Harper, the Nationals optioned left-handed reliever Xavier Cedeno to Triple-A Syracuse.
Cedeno pitched in one game during his third stint in the majors this season. He threw a scoreless inning on Saturday against the Chicago Cubs.