The left-hander lasted only 3 2/3 innings in San Diego's 7-1 loss to Miami on Saturday night in front of 19,266 fans at Marlins Park.
The defeat drops the Padres to 15-23 on the road.
Stults suffered through a rough outing, giving up six runs (five earned) on seven hits, both walking and striking out two in his shortest start since logging three innings as a Dodger on May 30, 2009.
His season-worst outing ended a streak of six consecutive quality starts and marked the first time he surrendered five or more runs in a game since back-to-back starts against the Giants on April 21 and April 27.
"It definitely wasn't the way I wanted it to go," Stults said. "I struggled with command of a lot of my pitches. Even the good pitches I made, they were able to put the barrel on the ball and find some holes."
San Diego manager Bud Black added: "There are those nights where ground balls go through. He makes a good pitch, and they loop it into center. They loop it into left."
The Marlins got going against Stults early.
Justin Ruggiano and Ed Lucas knocked Stults changeups into the outfield grass to lead off the bottom of the first. After Stults managed to retire Giancarlo Stanton, Marcell Ozuna got the scoring started with a single to center.
Matters worsened for San Diego as center fielder Alexi Amarista misplayed Ozuna's base hit, allowing both runners to score while Ozuna reached third base standing up.
"He tried to catch that ball, get it out of his glove and get the play to third," Black said. "He made a physical error. Trying to be a little bit too quick. Maybe not playing the ball as fundamental as you should, but that happens. We're a good defensive team."
Stults ceded a third run in the first when Ozuna scored on a Placido Polanco sacrifice fly caught by a diving Will Venable in right field.
Polanco's fly ball was right down the right-field line, and Venable landed on the chalk when he made the catch. Even replays could not pinpoint whether the ball would have landed in fair or foul territory had Venable let it drop.
"I'm supposed to catch the ball," Venable said. "Late in the game, maybe it's different, but I really didn't think anything of it until afterwards. ... I'm not about to let that ball fall. Then I'd really be in trouble."
After the three-run first, Stults seemed to settle into a groove. He needed only 22 pitches to get through the second and third innings.
However, the fourth inning played out much like the first.
Stults put the leadoff man on base, issuing a four-pitch walk to Polanco. Then, Stults threw a wild pitch to Derek Dietrich, putting Polanco in scoring position.
What followed were back-to-back-to-back singles from Dietrich, Adeiny Hechavarria and Jeff Mathis, doubling Miami's lead to 6-0. Hechavarria's hit scored Polanco, and Mathis brought Dietrich and Hechavarria home with a single.
After a sacrifice bunt from Turner and a Ruggiano strikeout, Stults walked Lucas, ending his night.
"I just didn't feel like I could command my pitches tonight like I had been feeling," Stults said. "I had a pretty good stretch of starts here where I felt really good just with my delivery. Something was a little bit off."
While Stults lacked command, Turner's was spot on.
Although the 22-year-old hurler gave up seven hits, he needed only 90 pitches to navigate eight innings. He struck out seven batters and walked only one.
"You can watch all the video you want, you can see the delivery, but once you get in that box and see the stuff, that's when it comes to life," Black said. "He threw a good game, but any time a team faces a guy for the first time, if the guy pitches well and hits his spots, the advantage usually goes to the pitcher."
The lone damage the Padres managed against Turner was a fifth-inning RBI double off the bat of Nick Hundley. Venable scored on the two-bagger after leading off with a triple to center field.
The right-hander ran into some trouble in a 21-pitch ninth, but he battled through the final frame to finish off his first career complete game.
While Turner enjoyed another great outing, an uncharacteristic performance by Stults made the difference Saturday.
"Hopefully, Eric makes 33 starts and the greater majority of them are like the ones he usually gives us," Black said.