Gunnar Henderson led off Baltimore's five-run first inning with a home run and the host Orioles went on to defeat the Seattle Mariners 9-2 in Friday night's series opener.

Colton Cowser added a two-run double in the opening inning, and Henderson later smacked a run-scoring triple during the Orioles' four-run seventh inning.

John Means (2-0), in just his third outing of the season, worked six strong innings for Baltimore, giving up two runs on six hits. He walked none and struck out four.

It wasn't how the Mariners wanted to begin a 10-game road trip after coming off a 4-2 homestand. Dylan Moore homered and doubled for Seattle.

Bryce Miller (3-4) took the loss, though he lasted 5 1/3 innings after the shaky first inning. He gave up five runs (four earned) on six hits and one walk, striking out one.

Six of the Orioles' 10 hits went for extra bases. Baltimore had scored a total of seven runs in its previous three games combined and had scored at least nine runs only twice in the past month.

Henderson's 13th home run of the season moved him into a tie with Houston Astros outfielder Kyle Tucker for the top spot in the major leagues.

Jorge Mateo and Henderson roped back-to-back triples in the seventh inning. Later in the frame, Adley Rutschman and Austin Hays provided run-scoring doubles. Rutschman and Cowser finished with two hits apiece.

Means was in the starting role after the Orioles revamped their rotation. They had played only one game since Monday.

With a fresh bullpen, Baltimore used four relievers.

Seattle led 1-0 when Moore, the first batter in the game, doubled and scored on Mitch Garver's one-out single. Moore provided the other Mariners' run when he hit his fourth homer of the season with two outs in the fifth inning.

Cal Raleigh joined Moore with two hits for Seattle.

Seattle pitchers recorded only two strikeouts, both against Kyle Stowers.