Shelby Miller is still without a win a month into his time with the Arizona Diamondbacks. The team's general manager thinks the right-hander is putting too much pressure on himself after being the centerpiece of a major December trade.

Diamondbacks general manager Dave Stewart told SiriusXM MLB Network Radio on Sunday morning that Miller is trying to live up to the hefty price the team paid to acquire him from the Atlanta Braves. The Diamondbacks' package to Atlanta included shortstop prospect Dansby Swanson (the No. 1 overall pick in the 2015 draft), outfielder Ender Inciarte and pitching prospect Aaron Blair.

"Shelby Miller, I think it's more, really, he's just feeling some pressure: of the trade, the players that we traded for him, trying to fit in," Stewart told MLB Network Radio. "I think the whole ordeal has just been different for him than it was leaving St. Louis going to Atlanta."

Miller, 25, lost an National League-worst 17 games last season with the Braves after they acquired him in a trade that sent outfielder Jason Heyward to the St. Louis Cardinals. But he had a 3.02 ERA in a career-best 33 starts for the Braves, who finished last in the NL East (67-95) and scored an NL-worst 573 runs, offering little offensive support to the pitching staff.

On Sunday afternoon, Miller again struggled, failing to make it out of the fourth inning, and fell to 0-3 as the Diamondbacks lost to the Colorado Rockies 6-3. Miller's ERA is 8.49 through six starts.

Shelby Miller is 1-6 with a 7.09 ERA in 10 starts during his first season with the Diamondbacks. Mark J. Rebilas/USA TODAY Sports

"We are trying everything. We are working with him," Diamondbacks manager Chip Hale said after Sunday's game. "We want him to stay positive. It's tough. "He's not very happy about it."

Miller and right-hander Zack Greinke were acquired by the Diamondbacks in the offseason to bolster the rotation. With that came expectations for the team to win.

Stewart said he has talked to Miller about the pressure and advised him to lean on his teammates.

"We've got ... four other guys in the rotation. I like our rotation. The reason why you have five starters is that one guy carries the weight one day and the next guy passes it on. So we've got time for him to fix whatever it is that's going on.

"If it's pressure, then there is no pressure. Take it off yourself and just go out there and be yourself and do what you're capable."

On Sunday, Miller gave up three runs on four hits and four walks. He walked the Rockies' Charlie Blackmon with the bases loaded in the fourth to make the score 3-1 for Colorado, then was taken out of the game.

"In the fourth inning, I rose my pitch count up and gave up some hits. Got into a jam and couldn't get out of it. Other than that I felt that I did all right," Miller said Sunday. "It's kind of the way the year has been going ... It's kind of killing me. One big inning."

The Associated Press contributed to this report.