DENVER (AP) — For a struggling Edinson Volquez, this was at least a step in the right direction.

Volquez threw five effective innings as the Cincinnati Reds wrapped up a long road swing with a 4-1 loss to the Colorado Rockies on Sunday.

“He had good tempo,” Reds manager Dusty Baker said. “He threw the ball better.”

Volquez (5-5) was making his first start since July 5 in what’s been an up-and-down season. He didn’t allow a hit until Ty Wigginton’s solo homer to left in the fourth. Volquez later gave up an RBI single to Jordan Pacheco.

Other than that, Volquez was solid, even if he struggled with his breaking ball in the thin air at Coors Field.

“Today, I was trying to throw my curve and it didn’t break like I wanted,” said Volquez, who allowed two earned runs.

Volquez, Cincinnati’s opening-day starter, has bounced around between the Reds and Triple-A Louisville this season in an effort to find his command.

The righty walked four and struck out three against Colorado. It’s the eighth time in 17 starts this season that Volquez has walked at least four batters.

Cincinnati’s offense couldn’t bail him out as it struggled against prized prospect Drew Pomeranz, who pitched five shutout innings in his major league debut.

Pomeranz (1-0) was a key piece in the deal that sent ace Ubaldo Jimenez to Cleveland at the trade deadline. He showed why the Rockies coveted him, allowing just two singles to Chris Valaika, who left in the fifth with a strained right knee.

Chris Heisey added a triple in the seventh — only to be stranded — and Joey Votto homered in the ninth as the Reds concluded their trip with a 4-5 mark.

“We just didn’t have a bunch of offense today,” Baker said. “They looked like they were at the end of a 10-day road trip.”

Pomeranz threw only 63 pitches before leaving in the fifth. He’s three weeks removed from an emergency appendectomy and is still building up his arm strength.

The lefty hasn’t pitched in many games since he was acquired in the five-player deal with the Indians in late July. Because a drafted player can’t be traded within a year of his signing, Pomeranz wasn’t allowed to join the Rockies organization until Aug. 17.

Instead, he threw off a mound in Arizona to keep his arm sharp. He made his first start for Double-A Tulsa on Aug. 17, throwing seven scoreless innings.

A few days later, he underwent an appendectomy that slowed his promotion to the big leagues.

Upon his return last week, Pomeranz tossed three scoreless innings for Tulsa before having his contract selected by the Rockies on Sunday.

Although Pomeranz wasn’t overpowering, he kept the Reds off balance with an effective changeup and a 91 mph fastball.

And when Pomeranz found himself in trouble early, he wiggled free by getting the Reds to ground into double plays in the second and third innings.

“We only got two hits, so you have to be impressed,” Baker said.

This was precisely the type of performance Rockies manager Jim Tracy envisioned from Pomeranz. Tracy caught a glimpse of him during spring training and was instantly intrigued, even asking around about the pitcher who was hitting 95 mph with his fastball.

“That’s how much he jumped out at me,” Tracy said.

After the game, Tracy said he was thrilled with Pomeranz’s ability to stay within the moment and not get rattled.

“I see a very, very slow heartbeat,” Tracy said. “It’s very encouraging to see.”

The banged-up Rockies went with a patchwork lineup Sunday, with All-Star shortstop Troy Tulowitzki (sore hip), first baseman Todd Helton (stiff back) and second baseman Mark Ellis (neck) all sitting out.

Just before the game, Carlos Gonzalez also was scratched with lower back stiffness and Wigginton went in to play left field.

NOTES: Players and coaches for the Rockies and Reds held a giant American flag in the infield during a tribute to honor the 10th anniversary of the Sept. 11 terrorist attacks. … The Reds will start LHP Dontrelle Willis on Monday against the Chicago Cubs. … Cincinnati 2B Brandon Phillips was given the day off. … Of Votto’s 28 homers this season, 15 have come on the road. … Rockies 2B Eric Young Jr. had three stolen bases.