Another go-round for rotation woes as Dodgers’ winning streak is snapped

The carousel that is the Dodgers’ starting rotation began to spin in May, when Ross Stripling faded and the team elected to shut him down for June. It spun when Alex Wood injured his elbow and when Mike Bolsinger combusted. And it will continue to spin beyond Friday, when spot starter Nick Tepesch stumbled through a brief, bullpen-taxing outing in an 8-6 defeat.

Called upon in the morning, Tepesch lasted only four innings in the evening. He dumped his team into a four-run hole in the second inning and exited with five runs charged to his tab. His temporary teammates could not compensate for the performance, and Manager Dave Roberts found himself as exhausted as his bullpen.

“We’ve tapped into our depth with the starting staff,” Roberts said. “I’ll say that.”

Tepesch may not be on the Dodgers’ roster by Saturday. But the trouble caused by the back of the team’s rotation may linger. The club may shut down 19-year-old rookie Julio Urias after his start next week. Brandon McCarthy and Hyun-Jin Ryu, both of whom are rebuilding strength after surgery, should fill the two openings. The two veterans offer talent, but still lack reliability, a reality for any pitcher returning from the operating table.

And so Roberts and his relievers may slog through more nights like Friday. The defeat ended a six-game winning streak for the Dodgers (41-34). Louis Coleman gave up two runs in the fifth and Chris Hatcher allowed a solo homer in the seventh. That nullified a night in which Corey Seager matched a career high with four hits, Justin Turner drove in two runs and Yasiel Puig hit a home run.

To Roberts, the stress stems from the rotation. Even during the winning streak at Dodger Stadium, the starters put the bullpen under duress. Besides Clayton Kershaw, the starters average 51/3 innings per game. Roberts knows that cannot continue.

“You’ve got to rely on your starters,” Roberts said. “You have to rely on your starters. I know that. I know the starters know that.”

The Dodgers turned to Tepesch out of something resembling desperation. The organization deemed Bolsinger unfit for a rotation spot last week. The team chose to option Carlos Frias earlier this week. On the farm, Jose De Leon has not stretched out beyond four innings and Jharel Cotton is not on the 40-man roster.

The main reason for Tepesch’s presence was the rib cage of Frankie Montas. The Dodgers intended to start Montas, a 23-year-old right-hander, on Friday. But he suffered a broken second rib while pitching in the minors, a complication from rib section surgery he underwent in February. He will be sidelined for four to eight weeks, according to a person with knowledge of the situation.

With 17 games without a day off before the All-Star break, the Dodgers elected to give the other starters an extra 24 hours of rest. That left Tepesch as one of only a few options. Texas released him on June 4; the Dodgers signed him two days later.

Tepesch posted a 2.00 earned-run average in three starts for triple-A Oklahoma City. A few hours before the game, Roberts offered a tepid endorsement.

“Really, I don’t know a whole lot about Nick,” Roberts said. “He’s a big guy. He’s performed well in triple A since we got him. He’s made 39 starts. So I’m just as curious as everyone is.”

Roberts did not have to wait long for an answer. The Pirates battered Tepesch in the second inning. He surrendered a leadoff double to outfielder Matt Joyce, and then a pair of singles. The second, by infielder Sean Rodriguez, drove in two runs.

After a pair of strikeouts, first baseman John Jaso knocked in Rodriguez with a single. The rally ended after outfielder Starling Marte doubled in the fourth run.

“He got ahead of guys, but just couldn’t put them away,” catcher Yasmani Grandal said.

The Dodgers cut into the deficit in the third. Seager and Turner hit back-to-back doubles for one run. Pirates starter Jameson Taillon slipped while delivering a pitch, a balk that brought Turner in from third.

Tepesch lacked the weapons necessary to disarm major league hitters. He also made mistakes. He paid for one in the third inning, when Pirates shortstop Jung-Ho Kang boomed a waist-high slider just inside the left-field pole.

“I made some bad pitches up in the zone,” Tepesch said. “And they took advantage of it.”

The homer ended the damage allowed by Tepesch. Coleman struggled with his command in the fifth. Hatcher served up a homer to Joyce.

Roberts could not condemn his bullpen. The group had had a heavy workload in recent days. He understood the source of the trouble.

“We’ve got to get length from our starters, consistently,” Roberts said. “Anything outside of that is not a formula to sustain winning. I’ll leave it at that.”

Andy.mccullough@latimes.com

Twitter: @McCulloughTimes