His fortunes appeared likely to change against the Diamondbacks, a team he had a 6-0 record against.
That hope was washed away in the second inning, when the D-Backs raked Richard (0-4) for six runs on five hits en route to an 8-1 victory that snapped a season-high four-game losing streak.
D-Backs left-hander Patrick Corbin (4-0) gave up one run and five hits while striking out seven. He walked three while his ERA dropped to 1.80. Corbin has opened the season by pitching at least six innings and allowing two runs or less runs in his six starts—all Arizona victories.
He lost his shutout bid with two out in the seventh when Chris Denorfia hit his second homer into the second deck in left field. Denorfia also had a double.
Richard was knocked out in the fourth inning after giving up seven hits, seven runs, five earned. He walked four and also committed a throwing error that preceded A.J. Pollock's two-run double in the second.
Richard has pitched more than five innings only twice in six starts and may be in jeopardy of losing his spot in the Padres' rotation.
"I'm not going to give you an answer now," Padres manager Bud Black said when asked about Richard's status.
Asked if Richard will make his next start, the manager said, "we're going to talk about that.
"The inability to consistently throw a strike when he needed to make that one pitch to get him out of a jam is not happening," Black said.
"I'm not throwing well," Richard said. "I don't think it's anything past that. As a starting pitcher it hurts to put your bullpen in a situation like that, it's disappointing."
Heath Bell, the former Padres closer came on in relief of Tony Sipp in the eighth with the bases loaded to get Jedd Gyorko to ground into an inning-ending double play. Bell pitched a scoreless ninth.
Paul Goldschmidt drove in a pair of runs for the D-Backs with two sacrifice flies and also had a single and a walk.
The win was the D-Backs' fourth against the Padres in 14 games. The loss was the Padres third in their last 10 games.
NOTES: D-Backs INF Didi Gregorius, who was reinstated from the seven-day DL Saturday after sustaining a mild concussion when he was hit in the head April 26, got hit in the left leg during his rehab at extended spring training in Phoenix. "I stayed in there because I really wanted my at-bats," Gregorius said. He has hit safely in his first seven games with the D-Backs. ... D-Backs OF Alfredo Marte was optioned to Reno, where he was scheduled to play Saturday night. ... D-Backs catcher Miguel Montero, who had a home run Friday night, was given the night off Saturday and replaced by Wil Nieves. D-Backs manager Kirk Gibson said Montero will start Sunday. ... Padres LF Carlos Quentin was back in the starting lineup after a balky right knee sidelined him Friday. Padres Chase Headley, who had a single, extended his hitting streak to nine games. ... The official scorer changed a ruling from Friday night's game giving an error to D-Backs center fielder Gerado Parra in the seventh inning.