Hernandez (6-3), who had won only once in seven starts after a 4-0 April, allowed a run on seven hits through seven innings. He walked two and struck out five. Mariners starting pitchers have now allowed three or fewer runs in a club-record eight straight games, and Seattle is 5-3 over that span.
The body of work was impressive Wednesday night, but it was Hernandez's ability to bear down in the first and work out of a jam that set the tone.
Brian Roberts led off by doubling to right field and Adam Jones drew a walk. With runners at first and second, Hernandez handled the meat of the Orioles order, getting Nick Markakis to fly to center, coaxing a grounder to first from Aubrey Huff that moved both runners into scoring position and then inducing a Melvin Mora bouncer to first for a 3-1 putout.
"You can see it in his emotion out there -- he's refining that, even," Mariners manager Don Wakamatsu said. "It's not out of control and he seems to be able to step off, focus and go right at them. Huge situation and he kept the momentum going on our side."
Once he worked out of trouble, Hernandez felt like he was in command. He improved to 4-0 at Camden Yards, a bandbox that's notoriously unkind when a pitcher makes a mistake.
But his tone-setting first inning thwarted Baltimore until Lopez woke up the Mariners' offense.
"The first inning, if they don't score any runs, now I got 'em," Hernandez said. "Now I have to pitch with more confidence and be better."
Wakamatsu was impressed that Hernandez kept pumping fastballs to challenge the Orioles, but more pleased at how the right-hander's sinker and changeup worked well as complimentary pitches.
"A lot of that was trying not to be too tricky, in a sense -- to be able to go at hitters a little more," Wakamatsu said. "He's got good enough stuff. His sinker's good enough that he can start it in the middle of the plate and then let it run off."
In evening its record on a nine-game road trip at 1-1, Seattle moved within one game of .500 at 29-30. The Mariners haven't been at .500 since May 10, when they were 16-16. A lot of the offensive burden was shouldered by Lopez, who had three hits and was in the middle of all of Seattle's scoring.
Lopez ripped a solo home run, his seventh of the season, to left field with one out in the second off Jeremy Guthrie. The Mariners got an unearned run in the fourth. Adrian Beltre reached on an error by third baseman Melvin Mora to lead off the inning, moved to third on Lopez's one-out single and scored on a groundout by Yuniesky Betancourt to go up, 2-0. The Orioles cut the lead in half on an RBI single by Roberts in the fifth.
Lopez remembered how Guthrie threw him a steady selection of sliders when he last faced the Mariners. So he was ready when Guthrie tried to employ the same strategy.
"I waited, he threw it and I tried to kill it," Lopez explained.
Lopez connected again in the sixth, after Russell Branyan led off the inning with a double to right. With one down, Lopez completed his third career multiple-homer game by hitting a two-run shot to left for a 4-0 lead.
Both of Lopez's homers came on 0-1 pitches, but Seattle hitters weren't overaggressive at the plate. Most teams hold hitters' meetings on the first day of a new series; Seattle's hitters met pregame to go over how to approach the Orioles.
"It's an aggressive offense that gets us in trouble," Wakamatsu said. "Obviously, put pitchers in a little bit deeper counts and getting them out of the ballgame earlier was one of the focus points of our meetings."
Once he had the lead, Hernandez assumed control. Sean White worked the eighth and David Aardsma pitched the ninth for his 10th save.
"I'm more relaxed, more confident," Hernandez said. "When you get the lead, you got to pitch. ... If they score runs [on offense], you do your job."
Guthrie (4-6) gave up four runs, three earned, on six hits in six innings. He walked none and struck out two. The Orioles have dropped six of seven.