DENVER -- Veteran right-hander José Ureña has gone from a possible answer for the Rockies’ rotation to one of many vexing issues.

On Saturday night, Ureña’s six solid innings were undone by three pitches -- solo homers in the first and third by Emmanuel Rivera and a two-run shot in the fifth by Josh Rojas -- in a 6-0 loss to the D-backs at Coors Field.

Ureña could not give up one run, much less four -- not with Arizona righty Zac Gallen throwing seven scoreless innings of two-hit ball. Gallen has a 1.14 ERA over his past four starts, and he holds a 2.03 ERA in five career starts at Coors Field. The Rockies finished with three hits, trudging away after D-backs rookie Alek Thomas reached above the center-field wall to snatch a probable homer from C.J. Cron.

But this is more about the future and Colorado's continued search for quality and depth in the rotation. For now, Ureña -- who is turning 31 on Sept. 12 and will be a free agent this winter -- is simplifying his task to keeping his pitches low. Ureña struck out five and induced six groundouts. But the three balls that sailed over the fence are the pitches he wants to avoid, even though Denver’s fly-ball-friendly atmosphere had as much to do with Rojas’ homer as pitch location.

“With my mechanics, I feel I’ve been on top of the ball, but sometimes the ball goes side to side,” Ureña said. “That’s not how I want the ball to go.”

Manager Bud Black’s level-headed critique?

“A lot of times you look at Major League box scores at a starting pitcher who goes six and gives up four, he might get a win -- the team might win,” Black said. “Tonight, it didn’t happen. His stuff was good -- crisp fastball, quality. He kept the ball down for the most part.”

Ureña spent the season’s first month in the Brewers’ bullpen before getting released. The Rockies signed him and saw strong results after bringing him to the Majors on June 6. In his first three starts, Ureña posted a 1.45 ERA over 18 2/3 innings. However, Ureña yielded six runs (five earned) in 5 1/3 innings at Milwaukee in his first start after the All-Star break. It started a stretch of five starts (including Saturday’s outing) during which Ureña’s ERA is 7.68.

Before signing Ureña, the Rockies had only one starter -- rookie Ryan Feltner, who has bounced between Triple-A Albuquerque and the Majors -- behind their Opening Day five-man rotation. Peter Lambert was not an option because of his lengthy recovery from Tommy John surgery, and two prospects -- lefties Ryan Rolison and Helcris Olivarez -- came down with shoulder injuries in Spring Training.

Because of their iffy depth, the Rockies needed good fortune, even after signing Ureña. But after his six scoreless innings against the Pirates on July 16, Colorado had reason to believe Ureña could add production.

But Ureña's past two starts -- both Rockies losses to the D-backs -- have been a mixed enough bag that it’s difficult to evaluate.

After giving up only two homers in his first six Colorado starts -- three at Coors Field -- Ureña yielded two last Sunday at Chase Field. However, he left the game with a one-run lead, only to see the Rockies succumb, 6-4.

“The game plan was to get out there and attack -- the game before, I was a little wild,” Ureña said.

Saturday’s three homers -- a slider to Rivera in the first, fastballs for the other two -- came off pitches that were too high and caught too much of the plate by any evaluation. Rojas' blast, however, was a classic Coors Field homer.

“No chance … nothing you can do after you release the ball,” Ureña said.

For his part, Ureña does not feel haunted by Coors Field -- a good attitude to have if he and the Rockies have positive talks after the season. But he can’t fall into patterns.

“I don't think I’ve changed too much," Ureña said. "If you look at the game, every time I come out I’m aggressive with sliders. Now, I’m trying to incorporate some other pitches. I can’t keep it the same way.”

There is enough promise from Ureña to keep him in the rotation, but there are several areas in which he must improve for his future.

“The ball-strike ratio can be better -- the walks have crept in there,” Black said. “He must keep the ball down the way he did initially.”