Harper, who said he has felt no pain in his surgically-repaired left knee this spring, hit a two-run homer off Astros starter Brett Oberholtzer in the first inning.
''I've felt great,'' Harper said. ''I've had zero pain on it. I've been able to do everything I've wanted to do. It's felt really good. I'm excited about that.''
That it came against a left-hander is a good sign for the lefty swinging Harper, who struggled against them last year. He has a career .229 average against left-handers as opposed to a .292 mark against righties.
''I hit lefties pretty good,'' Harper said. ''I always have. Last year, my knee killed me. I couldn't stay back on lefties. I was killing myself on that. It's going to be a little bit different this year.''
Ramos followed three batters later with a three-run drive that went over 400 feet and might have gone out of Space Coast Stadium. The wind was blowing at 16 mph but Ramos didn't need help with this shot.
''I heard it (but) I couldn't even see it,'' Nationals starting pitcher Tanner Roark said. ''I saw a guy in the beer deck look behind him and I went, 'Wow.'''
Nationals right-hander Doug Fister was scratched from his scheduled start because of inflammation in his elbow. Manager Matt Williams says he'll ''push him (back) a couple of days, just to make sure; get it out of there.''
Washington closer Rafael Soriano saw his first action of the spring and gave up two runs on three hits in one inning.
First baseman Marc Krauss went 3 for 4 with a home run for the Astros. Carlos Corporan had two RBIs.
Nationals: Roark gave up one run on four hits while striking out three in 2 2-3 innings. It was the first start of the spring for Roark, who moved into the spot when Fister was scratched.
Astros: Oberholtzer was tagged for six runs -five earned - on five hits, including the home runs by Harper and Ramos.
''I still need a little work mechanic-wise, timing my landing leg and following through,'' he said. ''I left a lot of balls up, off-speed and fastballs. I was a little shaky out of the gate and I just couldn't stop the bleeding.''
Oberholtzer did feel good about retiring the side in order in the second inning. Astros manager Bo Harper said he was impressed with the way the left-hander did not let the home runs affect him.
Nationals: Although the daily pitching schedule lists him as throwing a bullpen session Saturday, Washington is still unclear about the status of right-hander Ross Ohlendorf, who left Thursday's outing against the Braves with a back spasm.
''He's looking better today, but he had a pretty good spasm (Thursday) night,'' Williams said ''We'll continue to treat him and see where he lands (for) his next time out.''
Astros: Outfielder Dexter Fowler should be ready to return to the lineup Saturday. Porter indicated Fowler - who left Wednesday's game with a sore neck - could have played Friday. However, rather than have Fowler have to endure the bus trip to Viera, Porter chose to leave him in Kissimmee so he could get an extra day of treatment.
Outfielder Adron Chambers made his spring debut for the Astros after recovering from a hamstring injury. He went hitless in his only at-bat.
NEXT UP FOR NATS
Taylor Jordan was scheduled to start Washington's split-squad game at St. Louis on Saturday, but Williams said he wanted to get another look at the young right-hander. Instead, Chris Young will start against the Cardinals while Jordan will follow starter Ross Detwiler in a home game against the Braves.