Germán Márquez showed flashes of his potential in the first inning on Sunday.

He started his day by striking out Cooper Hummel on three pitches, then got two quick groundouts. It was that type of inning that has eluded Márquez this season, as, aside from his first start of the season, Márquez has been anything but sharp.

Chad Kuhl, after putting all the pieces together, is thriving for the Rockies

But then came the second inning, and things plummeted out of control again. He gave up four runs — three of which were earned, one that was off his attempted pickoff error — as the Diamondbacks beat the Rockies 4-0 to win the series. The Rockies now head to San Francisco for the start of a three-game series on Monday.

Márquez showed improvements overall on Sunday, but was still not his best. Diamondbacks starter Zac Gallen, in contrast, easily shut down the Rockies offense.

“I thought he was crisper with the fastball, his slider was good,” manager Bud Black said to reporters about Márquez. “He was out-pitched by their guy. We just couldn’t solve him.”

Márquez stayed in Denver this offseason, hoping that training at altitude would ease the transition out of spring training. He had trouble adjusting at the start of last season. He worked out at Coors Field with Rockies’ trainers until the lockout came, but then had to resort to hopping around from facility to facility. Most of those were indoors, and space was limited. Márquez also took a trip home to Venezuela, also interrupting his training schedule.

“He was the one guy that suffered more than others from the lockout,” Black said earlier this week.

Márquez stumbles through another start as the Nationals beat the Rockies 10-2

The statistics from his first start seemed good — he gave up just one run on three hits in seven innings against the Dodgers — but Black still didn’t think his stuff was crisp. Things went downhill from there.

On Sunday, Márquez sped through the first, but was picked apart in the second. Sterling Marte hit a double and Geraldo Perdomo drew a walk to get two on base. Márquez then made the mistake of pitching one to the center of the zone, and Nick Ahmed took advantage, hitting an RBI single. The Diamondbacks scored two other runs in the second off a double from Jośe Herrera, their rookie catcher who had only 25 at-bats heading into Sunday’s contest. The Rockies gave up one more run in the fifth after a pickoff throwing error from Márquez.

The root of Márquez’s problem is his fastball command. He’s been tinkering with a new four-seamer, but has yet to find success with it. It’s a difficult balance: the Rockies want him to be constantly evolving his game, but they also need their top pitcher to play to the best of his ability. They scaled him back, urging him not to use his new stuff in a game as much and to instead throw it during side sessions until he’s more confident.

The best version of his fastball is the one he can throw the hardest, Black said. On Sunday, Márquez threw a 98.1 mph sinker to strike out Ketel Marte in a 1-2-3 fourth inning, a glimpse into what Márquez can do when he’s at his best. He start overall was an improvement of his last four — had seven strikeouts, a season-high — but he still walked four, also a season-high.

“I think he can be an All-Star every year,” Black said. “He has to pitch well, but he has that talent. The expectation that players put on themselves sometimes get in their way. He wants to get better, he expects to get better. But I think he’s trying to do too much.”

Colorado Rockies pile on five runs in the fourth to beat the Nationals

On Sunday, the Rockies’ offense once again provided its pitching staff with no support. Gallen breezed through his seven innings of work. Jose Iglesias had two hits, while Connor Joe, Yonathan Daza and Charlie Blackmon each had one.

Roster news

The Rockies made a reliever swap on Sunday, sending RHP Justin Lawrence to Triple-A in exchange for LHP Lucas Gilbreath. Gilbreath started the season on the COVID-19 list and struggled in his return, making four appearances before he was sent down.

Kris Bryant, out with a back strain, will remain in Arizona after the Diamondbacks series to continue rehabbing at Salt River Fields, the Rockies’ spring training facility. He has not played since April 25, and, while improving, has not swung a bat since the injury.