The unraveling of Hernandez's afternoon happened in a flash. Ender Inciarte singled to lead off the game. A.J. Pollock doubled down the left-field line to put runners on second and third. Paul Goldschmidt singled to left to put Arizona up, 2-0. Hernandez got his first out by fanning David Peralta, but then catcher Welington Castillo, who was on the Mariners for six games before Seattle traded him to the D-backs in the Mark Trumbo deal, blasted a ball over the fence in left field to make it 4-0 .
Hernandez settled down a bit, only giving up one more run until the seventh, but Castillo got him again with a solo homer in the fourth and the D-backs tacked on two more in the seventh.
Hernandez's outing wasn't as bizarre as his June 12 effort in Houston, when he gave up eight earned runs on five hits in one-third of an inning and departed after throwing 31 pitches. That was, quite simply, the worst performance of Hernandez's career. But this one led to the same result, a loss, and now the Mariners are 46-56.
After the game, Hernandez stood at his locker and said there was a simple reason for what had occurred.
"I was making mistakes, that's all," Hernandez said. "Balls that were [supposed to be] on the corners were in the middle of the plate, and they put good swings on them."
Coupled with an aggressive approach by Arizona's hitters, who were swinging early and often, it made for a crooked linescore for Hernandez, whose ERA rose from 2.69 to 3.02 and who finally encountered trouble after a five-game stretch in which he posted a 1.09 ERA with 32 strikeouts and four walks in 33 innings.
"His command was off," Mariners manager Lloyd McClendon said. "His stuff was plenty good, but his command was off. A lot of pitches in the middle of the plate.
"He actually settled down in the middle innings, started to throw the ball pretty decent, and elevated again late. They're an aggressive club. You've got to make quality pitches. And we just didn't do it the last two days."
Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB. This story was not subject to the approval of Major League Baseball or its clubs.