Patrick Corbin's hot start to the season was cooled in a rainy 7-3 loss to the Orioles on Saturday night at Oriole Park at Camden Yards.

The lefty entered the night undefeated, at 2-0, with a 2.50 ERA. Corbin had allowed just five earned runs over his first four starts, and he was looking to carry the momentum of the Nationals’ blowout win from the previous evening.

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Instead, Corbin surrendered five runs off eight hits (including a fourth-inning home run to left-handed Rio Ruiz) in five innings -- his shortest outing of the season. He also issued one walk and struck out two batters -- the latter his lowest total since May 31 of last season.

“I was falling behind guys, and not being able to finish tonight was really what was going on,” Corbin said. “It seemed like from the start of the game and until I was done, just they had some long at-bats. I wasn’t able to put guys away, and just one of those nights where things weren’t really working for me.”

Corbin faced six Orioles in the opening frame, resulting in two doubles and a pair of runs. He pitched to five hitters in the second inning, and the Nationals' deficit grew to 4-0. In the fourth, Corbin gave up a Statcast-estimated 340-foot home run to Ruiz off a 78.7 mph slider. His evening concluded after ending the fifth with a couple of quicker outs.

“Corbin has one of the best left-handed sliders in the game,” Orioles manager Brandon Hyde said. “To be able to lay off that, see him up out over [the plate], our approach has been good.”

When Corbin's slider is on, it's on. Entering Saturday, opponents were hitting a mere .143 against it this season. Against Baltimore, he threw his slider for 35 percent of his pitches, resulting in 23 swings and seven whiffs.

“I thought his slider wasn’t as sharp as it normally is,” Nationals manager Dave Martinez said. “It was just up. When he tried to get it down, he threw it too far down. He got behind and left some balls up. My biggest thing with him is, I asked him if he was OK. He mentioned that this is the best he’s felt all year, so that’s good. His location was not good today. He battled through five innings. His pitch count got up, and we had to get him out of there.”

As the Nationals’ pitching staff has been hit with injuries -- including the recent decision to place Stephen Strasburg on the 10-day injured list -- Martinez has been looking for starters to go deeper into games in order to keep relievers fresh. Right-handers Javy Guerra, Kyle Finnegan, Dakota Bacus and Wander Suero made relief appearances on Saturday.

There is a balance, too, between maximizing the starters and not burning them out for the sake of sparing an inning from the bullpen. That was the case with Corbin’s exit after the fifth.

“We could see him throughout the innings fighting, and that’s uncharacteristic with him. When he’s sharp, he gives you that sixth inning,” Martinez said. “When they get up there at around 90, 95 pitches in five innings, that tells me things are not going to get better. To let them go out there for another 20 pitches doesn’t seem right. ... We don’t want those guys out there laboring through innings just to get the pitch counts up and try to build up innings for them, because when you start doing that, you risk a lot of injury.”

Even though Corbin was not able to pitch his way out of his struggles, he quickly and clearly identified where he needs to improve for the next start.

“It all just comes back to not getting ahead of guys, falling behind and putting them in hitter counts,” Corbin said. “That was the story of the night.”