Hernandez's first Rockies start came 10 days after he last pitched for the Twins, for whom he went 10-8 before Colorado claimed him off waivers on Aug. 6.
"I felt coming in, it was going to take two starts to get his feet underneath him," Rockies manager Clint Hurdle said. "He's in a lot better place now than he was when he joined us.
"I just felt he fatigued a little bit in the sixth inning. ... I think it was being away and still some residual rust."
The idea was to acquire Hernandez for a late push, but a lot will have to happen for the Rockies (56-69) to make one. They've won the first two games against the Nationals, who have lost nine straight, but still remain where they were when the series started -- nine games back in the National League West.
Hernandez displayed the change-of-speeds he has used to put together a solid career that includes a World Series Most Valuable Player Award in 1997 and solid work in the NL West.
"For me, I feel very good," said Hernandez, who pitched for the Expos/Nationals franchise from 2003-06, but has won five straight starts against the club since leaving. "I had a bad inning in the sixth. I felt a little bit tired in that inning. It's difficult when you feel tired. I was working a lot."
Troy Tulowitzki doubled and drove in three runs, two on a single in a fifth inning that saw the Rockies score six runs and take 11 turns at bat.
By the end of the fifth, everyone in the lineup but Matt Holliday and Clint Barmes had a hit. Holliday had drawn three walks and scored each time. Barmes would deliver an RBI single in the ninth.
The Rockies scored eight runs on seven hits in four-plus innings against Nationals starter John Lannan (6-12).
And even though even though they're just 22-40 away from Coors Field, the Rockies have won eight of their past 12 road contests. Lately, they've been taking advantage of scoring opportunities on the road -- a fact that makes the weak offense during a potentially season-killing 3-7 homestand last week even less explicable.
On Saturday, they went 8-for-15 with runners in scoring position.
"We were real good in our situational hitting opportunities tonight, very efficient -- two-out RBIs, got the barrel on a lot of balls," Hurdle said. "A real good night for us offensively. We needed to have one of those."