Collin McHugh threw seven solid innings, and Carlos Gomez delivered a two-run, go-ahead single to lead Houston.
"We just didn't do a good job," Hale said. "It's the way it goes. Sunday day game. Energy level wasn't great compared to the way we've been playing on this road trip. We'll have to get to the bottom of it and crank it back up for Washington. I was surprised we weren't more competitive today."
The streaky Diamondbacks entered the weekend as winners of six straight and eight of 11 following a six-game losing streak around the All-Star break. But after dropping a second consecutive game to Houston and losing the series, Hale pointed to the intensity.
On Saturday night, Hale benched Yasmany Tomas for a similar hustle-related issue after Tomas didn't sprint out a grounder to first base.
First baseman Jake Lamb said he was unaware of a lacking of energy in the game.
"Not that I can tell," Lamb said. "I can't speak on that. In the dugout, it's the same it's always been. Guys are still busting their butts and everything."
When asked about possible remedies for the upcoming four-game series in Washington, Hale was brief in his answer.
"Ask me tomorrow," he said before ending the interview. "That's it. I'm good."
Lamb put Arizona up 1-0 with an RBI double in the second, but Houston tied it in the bottom half on Carter's sacrifice fly.
"We had situations where we should have got some runs in, but we didn't get the runs in," Hale said. "We could have made the score a lot closer, but we just failed to do that. We have to tighten it up and play a lot better."
Robbie Ray (3-6) was tagged for four runs and seven hits with three walks and five strikeouts in five innings. Ray has allowed four or more runs in two of his last three outings — both losses.
"It's just tough when you've got guys on base and you're in those high-pressure situations all the time," Ray said. "Eventually, it's going to catch up to you."
Evan Gattis added a solo home run in the fifth to give Houston the three-run lead.
McHugh (13-5) won his fourth straight start, giving up one run and eight hits with six strikeouts. The right-hander, who is tied for the AL lead in wins with teammate Dallas Keuchel, has allowed two runs or less in three of his last four starts.
"You see why they're one of the best," Lamb said. "When they get that lead, they've got the offense to keep the lead, and they've got the pitching to shut the door."
Gomez, who was acquired Thursday in a trade with Milwaukee, gave Houston a 3-1 lead with a two-out, two-run single in the fourth. Houston had loaded the bases on a walk to Chris Carter, a single by Castro and Altuve was hit by pitch.
FIRST THINGS FIRST
Lamb played his first full game at first base, moving over from his usual spot at third base to allow Aaron Hill to play third and usual first baseman Paul Goldschmidt to serve as the designated hitter. Before the game, Lamb said he asked Goldschmidt for advice.
"I asked Goldy for tips, and he said, 'If you can play third, you can play first. It's a lot easier.' Coming from him, that helped," Lamb said.
COMING AND GOING
The Astros officially activated RHP Mike Fiers on Sunday after acquiring him and Gomez from Milwaukee on Thursday. Fiers will start Tuesday at Texas. ... RHP Vince Velasquez was optioned to Double-A Corpus Christi following Saturday's game to open up the roster spot for Fiers.
Diamondbacks: OF A.J. Pollock was out of the lineup for a second straight day Sunday after leaving Friday's game in the seventh inning with tightness behind his left knee. ... RHP Chase Anderson, who has been on the DL since July 19 with right triceps inflammation, was scheduled to start Sunday for the Arizona League D-backs and throw four innings or 60 pitches.
Diamondbacks: RHP Zack Godley (2-0) starts Monday in the first game of a four-game series at Washington. Godley, who has allowed three runs over his first two starts, will be opposed by RHP Doug Fister (4-6).
Astros: RHP Lance McCullers (5-3) starts Monday in the first game of a three-game series against the Texas Rangers in Arlington. McCullers has allowed three earned runs or less in 12 of his first 13 career starts. Texas will counter with RHP Colby Lewis (11-4).