BALTIMORE (AP) -- Buck Showalter counted himself among the many fans at Camden Yards pulling for Steve Johnson to excel in his first major league start.

Watching Johnson from the Orioles dugout, Showalter allowed himself to play the role of a baseball enthusiast while the rookie struck out nine Seattle Mariners during Baltimore's 9-2 victory Wednesday night.

''Stevie was good, huh? That was fun to watch,'' Showalter said. ''I tried to watch it as a manager trying to win a game but also a fan of those type of situations. We really wanted Steve to have success tonight, for him and for the club.''

Johnson (1-0) gave up two runs, five hits and two walks over six innings in his second big-league appearance. The 24-year-old was recalled from Triple-A Norfolk to sub for Tommy Hunter, who was scratched because he threw in the bullpen Tuesday night in anticipation of entering a game that lasted 14 innings.

Johnson grew up in Baltimore and is the son of former Orioles pitcher Dave Johnson, who now works for the team's TV network. Steve Johnson's debut as a starter came exactly 23 years after his father made his first career start in Baltimore, a complete-game win against Minnesota.

Although the younger Johnson didn't go the distance, the right-hander made the most of his 97 pitches.

''It was great and it was unbelievable. Words really can't explain,'' Steve Johnson said. ''I know a lot of people texted me and said they were coming. A lot of people from my high school and people I went to high school with. It was great.''

To cap it off, he shared an emotional moment with his father after the game.

''It's something I was thinking about for a long time - get my first win and have him here,'' Johnson said. ''And the way those days worked out, 23 years to the day, it's just special. It's all I can really say about it. It means a lot to me.''

Matt Wieters volunteered to catch the rookie, one night after stooping behind the plate for all 14 innings. In addition to serving as a calming influence while Johnson was on the mound, Wieters tied a career high with five RBIs to help Baltimore complete a three-game sweep.

Nick Markakis and Mark Reynolds homered, and Adam Jones had three hits for the Orioles, who have won five straight and eight of 10. It was Baltimore's 60th victory of the season, compared to 69 all last year.

The Orioles built a 7-0 lead by the fourth inning against former teammate Kevin Millwood (4-10) and cruised to the finish in their sixth sweep of 2012.

Johnson blanked Seattle on three hits through five innings before giving up a two-run homer to Kyle Seager in the sixth.

It was Seager's team-high 13th homer, the second in two nights. He finished with three hits in the Mariners' fourth straight defeat, a skid that began at Yankee Stadium.

''Tonight is the first night we didn't play well. We played well in New York and last night was a battle,'' manager Eric Wedge said. ''We're working through some things here. We have a couple of new guys, and we have to take an opportunity to see what they can and cannot do.''

Johnson needed only six pitches to strike out the first two batters in the first inning, then went to 0-2 on Jesus Montero before giving up a single. Johnson followed that with a three-pitch strikeout of cleanup hitter John Jaso.

Baltimore went up 2-0 in the bottom half. With two on and two outs, Wieters hit a liner to right that sent Eric Thames running toward the wall. As he leaped to make the catch, the ball popped out of his glove for a two-run double.

Seattle used a single and two walks to load the bases with one out in the second, but Johnson worked out of trouble.

The Orioles made it 4-0 in the third. Markakis led off with a triple and scored on a single by J.J. Hardy, who took third on a double by Jones and came home on a groundout by Wieters.

In the fourth, Reynolds hit a solo shot, Omar Quintanilla singled and Markakis drove a 1-2 pitch over the right-field wall. Millwood got the final two outs but did not return for the fifth.

''I didn't pitch very good today,'' said Millwood, who gave up two homers in a game for the first time this season. ''No fun to stink. We didn't play well here at all.''

Millwood pitched for Baltimore in 2010, going 4-16 with a 5.10 ERA in 31 starts.

Wieters hit a two-run double in the seventh off Josh Kinney.

NOTES: The Orioles placed INF Ryan Flaherty on the 15-day DL with a bacterial infection and recalled RHP Miguel Socolovich to strengthen the bullpen after Tuesday night's marathon. ... Seattle has a day off Thursday and will face the Los Angeles Angels on the road Friday. Baltimore opens a three-game series against the Kansas City Royals on Thursday night. ... Seattle's Michael Saunders went 0 for 14 with seven strikeouts in the series.