Here were the two biggest Draft picks in team history -- Strasburg the first overall pick in 2009 and Harper in '10; two faces of the franchise that had never faced each other before this exchange.
Fans leaned up against the chain-link fence surrounding the field, some rapidly snapping photos while others were content to simply watch.
Harper was first in a hitting group that included Denard Span and Danny Espinosa. The three hitters rotated after every five pitches, each seeing 10 in total from Strasburg and later closer Drew Storen.
Harper took a hard cut at the first fastball Strasburg threw him, but he missed. Harper swung at three of the 10 pitches from the righty, missing two and turning one into a line drive toward second base.
Afterward, Harper downplayed the exchange.
"I'm just up there to face live pitching and see some pitches, nothing else, really," Harper said. "If I get a hit or if I strike out, I don't even know. That [stuff doesn't] really matter. It's not a big deal to me."
Last season, Nats pitchers threw two rounds of live BP before games, but they were only scheduled to throw one this year. Strasburg delivered his first session on Sunday to a mix of Minor Leaguers and backups, but he wanted to throw one more before getting into a Spring Training game.
The righty mixed in his whole arsenal throughout his 30-pitch session.
"He looked good. I'm thankful he's on my team," Harper said.
Some of the veteran position players jumped at the chance to face another round of live BP in advance of the Nationals' first Grapefruit League game Thursday against the Mets (5:05 p.m. ET on Gameday Audio).
"It gives them the opportunity to get back in and see a little bit more [velocity], a little better movement on pitches in anticipation of Game 1," manager Matt Williams said. "For us, it's about work. It's about Harp seeing pitches. It's about Stephen feeling the pitches that he's throwing.
"There's nothing wrong with a little friendly competition once in a while, too."