PHOENIX -- The last time rookie right-hander Connor Seabold pitched for the Rockies, he had lost his changeup, which had been his best pitch before he arrived in an offseason trade with the Red Sox.

“I’ve got to find something,” he said.

Was Seabold angry? Down on confidence?

“A little bit of both,” he said. “We tried to make some adjustments. The arm slot on it is pretty low and we were trying to get it higher. That might have thrown it out of whack.”

Seabold mixed the changeup with the fastball and curve in a career-high 5 1/3 three-hit innings against the D-backs, while tying his season high with five strikeouts in Thursday afternoon’s 5-4 walk-off loss at Chase Field.

However, Pierce Johnson absorbed his first blown save in 12 opportunities as Corbin Carroll’s two-run single with two outs in the ninth gave Arizona a sweep of the four-game set.

Carroll’s hit sent the Rockies to their first loss when leading after seven (21-1) or eight (29-1) innings this season. It also negated a big day for some of Seabold’s fellow young players as Brenton Doyle and Nolan Jones each logged two hits and an RBI, while Ezequiel Tovar belted a seventh-inning solo homer.

The evaluation of the Rockies -- not only Thursday or for a single road trip, but for the season -- rests with how far younger players come.

Seabold was acquired for a player to be named or cash considerations with the idea of providing rotation depth. He pitched well enough in Spring Training to begin the season as a bullpen long man, but a run of injuries that currently has four starters on the IL gave Seabold a starting opportunity.

He joined the rotation on the run, which at times has stressed his arm. But he was fine for 92 pitches against the D-backs. Seabold didn’t show wear until the sixth, when he walked leadoff man Ketel Marte (who scored the only run charged to him), and saw Carroll sky a ball deep to center for an out.

“He’s a good kid -- as far as the makeup and the poise, he comes from a good college program [Cal State Fullerton] and he was developed the right way,” manager Bud Black said.

“We’ll see. I mean, he’s so young in his career, less than 10 starts counting some starts in Boston. He’s learning on the fly.”

After solid five-inning outings in his first two starts, Seabold didn’t make five innings in his next three and posted an 8.53 ERA. The adjustment to the Denver altitude may have figured in; however, one of the passable starts was at Coors Field and one of the awful ones was at Globe Life Field against Texas.

Arizona offered the best of both worlds -- on the road and at the Majors’ second-highest elevated park (granted, Chase Field is 4,100-some feet lower than Coors Field).

Seabold forgot about where he was pitching, bagged the talk about arm slots and “didn’t worry about much besides throwing it [the changeup] for a strike and just letting it eat.”

The D-backs had no momentum until Lourdes Gurriel Jr.’s two-run, sixth-inning double off reliever Jake Bird.

“Seabold pitched a really good game,” Carroll said. “I think we needed someone to get us going and [Gurriel] did just that.”

Only once, in the fifth, did Seabold work with more than one baserunner.

“There’s a reason I was preaching it so hard the past couple of weeks,” Seabold said. “That was the most complete my repertoire has been since Spring Training. It’s just throwing strikes and letting them get themselves out. I was missing some barrels.

“I’d like to not walk the leadoff guy in the sixth. That ended up hurting, but just getting into the sixth in the first place, that’s a new step for me.”