In a second inning that unraveled expeditiously, Grayson Rodriguez threw fastball after fastball.

He threw six to Nathaniel Lowe, and six more to Corey Seager. Both plate appearances resulted in walks. He threw four to Leody Taveras and three more to Jonah Heim. He threw more four-seamers than anything else — by a wide margin — and finally left the game after his final fastball turned into a single that drove in the fifth run of the inning.

Since Rodriguez returned to the Orioles’ rotation in July, the 23-year-old has found greater success by leaning on his four-seam fastball. That heater, which reaches and passes triple-digit velocities on the regular, carried him through the second half of his rookie campaign, in which he held a 2.58 ERA in his final 13 starts.

But when Rodriguez leaned on the fastball in Sunday’s 11-8 loss to the Texas Rangers in Game 2 of the American League Division Series, it belied all of that earlier success.

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By relying on it more than ever before in his career — while being seemingly unable to locate pitches — Rodriguez allowed Texas to wreak havoc on his postseason debut and put Baltimore in an early hole that would only grow deeper.

Rodriguez hurled fastballs with 44 (75%) of 59 pitches. He offered 11 changeups, two curveballs and two sliders. His changeup was especially good despite the little use, with six whiffs on seven swings.

“I think we were just trying to be aggressive and induce early contact,” Rodriguez said. “That’s what we were trying to do — make them put the ball on the ground.”

Rodriguez never found a way to use his high-upside secondary pitches with any regularity because his shaky fastball command left him behind in counts (he tied his career high of four walks). And, as he continued to throw heaters, the Rangers homed in. They loaded the bases in the first inning but couldn’t capitalize. They then chased Rodriguez from the outing just two outs later, setting up the stage for a defeat at Camden Yards that put Baltimore in danger of elimination.

“Things just happen that way sometimes,” infielder Jorge Mateo said through team interpreter Brandon Quinones. “He’s been pitching really well lately, and we know what he’s capable of doing.”

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The Rangers, who entered as one of baseball’s top hitting teams, opted for patience just as Rodriguez hoped to induce early contact. Rodriguez said he sprayed his fastball, not hitting spots as precisely as he has recently, but the game plan was clear: continue pumping fastballs. So he did.

“We had a plan, and we were going to stick to it,” Rodriguez said.

When catcher Adley Rutschman was asked the specifics of that plan, he smiled, noting that he can’t reveal much.

“It’s individualized for each hitter, and we were trying to work his fastball around,” Rutschman said.

In many ways, the outing from Rodriguez on Sunday had parallels to a previous matchup against the Rangers. Rodriguez, who grew up in Nacogdoches, Texas, and attended Rangers games, performed well enough in his MLB debut at Globe Life Field. But, in his second meeting with Texas, Rodriguez allowed eight earned runs in 3 1/3 innings — using his fastball 59% of the time.

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At the time, that was the most Rodriguez had used his fastball in any start. It would also be his last start for Baltimore until July.

Rodriguez was optioned to Triple-A Norfolk in late May. Once there, he dropped his cutter from his repertoire almost entirely to increase his focus on his best secondary pitches: the slider, curveball and changeup.

And, when Rodriguez returned, it was with improved fastball command and more reliance on the pitch.

“I think velo doesn’t really matter to big league hitters,” Rodriguez said Saturday. “They can pretty much hit 100 pretty easily, so the command is the big thing.”

In July, August and September, Rodriguez’s fastball usage increased, ending at 56.7% in the final month of the regular season. Over those three months combined, his fastball usage was 53.1%; in April and May combined, he threw his heater 44.8%.

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But, even as he threw his fastball more, Rodriguez needed that heater to get to his secondary pitches. Opposing batters hit .360 against Rodriguez’s four-seamer in September while hitting sub-.200 against his slider and curveball. The same trend applied in July and August.

Sunday’s 1 2/3 innings — the shortest start of his early career — was marred quickly. It was a disappointing result for a pitcher who redefined himself after a midseason demotion. And much of it was down to a fastball that is elite in smaller doses but became too frequent an offering against Texas.

“They got on his fastball early,” infielder Gunnar Henderson said, “and that kind of set them up.”