BALTIMORE -- By the time Drew Pomeranz took the mound at Oriole Park at Camden Yards on Friday night, the Giants had already built a five-run lead thanks to their most productive first inning of the season. It didn’t last long.

Pomeranz proceeded to give up a career-high eight earned runs, including six in the bottom of the first, over 1 1/3 innings, sinking the Giants in a 9-6 series-opening loss to the Orioles. The disastrous outing inflated Pomeranz’s ERA to 8.08 over 10 starts this season, likely putting his spot in the Giants’ rotation in peril.

Manager Bruce Bochy deflected a question about Pomeranz’s future in the rotation afterward, but the 30-year-old left-hander’s continued struggles, coupled with Dereck Rodríguez’s resurgence, could prompt a change during the Giants’ series in New York next week.

“The game just ended,” Bochy said. “I’ve got to sit on this. We’ll talk about what we’re going to do.”

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The Giants signed Pomeranz to a one-year deal in the offseason in the hope he would be able to bounce back from a disappointing season with the Red Sox and help stabilize the San Francisco rotation. But he has struggled to deliver so far, producing just one quality start in 10 outings this season.

Since firing six shutout innings against the Blue Jays on April 24, Pomeranz has allowed 25 runs over 14 1/3 innings (15.70 ERA) and failed to get past the fifth inning in each of those five starts.

“It’s been pretty [bad] the last few for whatever reason,” Pomeranz said. “My stuff’s felt pretty good. It’s just not making pitches when I need to. I’m not really sure what to say exactly. It’s been pretty frustrating.”

Pomeranz needed 56 pitches to record just four outs against the Orioles, who entered Friday with the worst record in the Majors. In the first inning, Pomeranz issued a one-out walk, followed by three consecutive singles that cut the Giants’ lead to 5-2. After striking out DJ Stewart looking, Pomeranz walked Keon Broxton to load the bases with two outs for Dwight Smith Jr., who crushed a 2-1 fastball over the center-field fence for a grand slam that put Baltimore ahead, 6-5.

“That’s hard to take because that’s been an issue with us,” said Bochy, whose club had scored just 12 runs in the first inning over the first 55 games of the season. “We go out and have our biggest first inning. You’d like to enjoy it for a little while, but we had about 10 minutes and it was gone. That’s frustrating for our guys.”

Mike Yastrzemski, after hitting an RBI triple in the first inning, briefly tied the game by launching his first career home run off Andrew Cashner in the second. But Pomeranz faltered again in the bottom half of the inning, surrendering a two-run home run to Trey Mancini on a 3-2 fastball and exiting with the Giants trailing, 8-6.

Rodriguez was summoned to replace Pomeranz and delivered 4 2/3 shutout innings in his second relief appearance of the season, bolstering his case for a return to the rotation. Pomeranz is due to make his next start on Thursday, but there’s no guarantee that he’ll be the one to take the mound at Citi Field.

As Rodriguez showed, the Giants have alternatives.