WASHINGTON — The first boos, guttural and loud in a mostly empty ballpark, greeted Bryce Harper during pregame introductions 15 minutes before the rain-delayed first pitch Tuesday night, as he stood in the Nationals Park visitor’s dugout wearing another team’s uniform.

Jeers again filled the chilly air when Harper walked to the plate as the No. 3 hitter for the Philadelphia Phillies in the first inning, his initial at-bat as a Nationals opponent. More hostility came while he awaited each pitch from Washington’s Max Scherzer, negativity interrupted only by the sheer-joy roars after each strike of his eventual whiff, which concluded with a swing-and-miss at an 85 mph changeup.

Harper had said he expected a mixed reaction from spectators in his return to D.C. after leaving via free agency to sign a $330 million, 13-year deal with the Phillies. Sure sounded rather one-sided from an announced attendance of 35,920.

Adding to the theatrics of it all, as is his wont, Harper delivered a no-doubt-about-it homer into the second deck off Jeremy Hellickson in the eighth inning, a two-run shot that traveled about 450 feet and put the Phillies ahead 8-2. That topped off a 3-for-5 showing with three RBIs, and Harper marked the moment with an epic, twirling bat flip in the direction of his former dugout, followed by elaborately choreographed celebrations with his current teammates .

In the bottom half of the first, there was booing as Harper headed out to play right field — where fans in the front row of the bleachers wore shirts that spelled out “T-R-A-I-T-O-R” — and when he caught Adam Eaton’s fly for the first out.