On a self-described "grind day," Shields suffered his first loss of the season after the D-backs made him throw nearly 30 pitches in the first inning and scored three runs with two outs in the third in an eventual 4-2 loss for San Diego to open a three-game series at Chase Field.
Shields' 7-0 start to the season in 14 starts was the best of his career, but he said he knew as he warmed up in the bullpen Friday it was going to take a workhorse effort to get to 8-0.
"It was one of those games where I had to grind it out," Shields said.
He did that for the most part.
The D-backs took a lead in the first on an RBI groundout by Paul Goldschmidt, but Shields worked around a pair of walks and a hit batter to strand the bases loaded. He threw 29 pitches in the inning, just 14 of which were strikes.
The real damage came in the third, when the Padres looked like there were going to get out of a jam thanks in part to a overturned call on a Pat Murphy replay challenge. But back-to-back doubles from Aaron Hill and Welington Castillo and a RBI single by No. 8 hitter Nick Ahmed to cap a nine-pitch at-bat put the Padres in four-run hole.
"It was a grind day and if I get [Hill] out right there it's a whole different ballgame," Shields said. "And Ahmed, I made my pitch and he hit it. Nothing you can do about it."
Shields said he hung a curveball to Castillo, but he did the same in the first inning and got the catcher looking.
"I think he'd like to take back a few pitches here and there," Murphy said. "It wasn't his best outing but he's a fighter. We could have done some things to help him a little bit more.
"We didn't play super defense behind him. There were little plays here and there that didn't show up as errors but we didn't play super defense behind him."
Shields gave up four or more runs four other times this season -- including May 8 when the D-backs scored five on four home runs -- but he was 3-0 with a no-decision in those games. He wasn't as fortunate Friday, when the Padres were 0-for-6 with runners in scoring position and left 11 on base in losing for the eighth time in 11 games.
"We're not happy with the way we're playing right now," Shields said. "It's kind of cliché but we do have a long season to play."
Chris Gabel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.