"Probably the best start of his career," said Danny Valencia.
"About as good as he's been," added manager Bob Melvin.
It was hard to argue against that line of thought, as Manaea himself confirmed it.
"It's definitely the best start I've had up here," the 24-year-old rookie said with a beaming smile.
He didn't earn the win for it, as Ryan Madson blew the save in the ninth inning before Valencia's late throwing error pushed across the winning run for Houston in the 10th. It couldn't completely detract from Manaea's day.
It was the heralded southpaw's second scoreless outing in three starts and a total 180-degree turn from the six runs he allowed to Minnesota in his last start.
"My last start wasn't the greatest," Manaea said. "It was pretty bad, but I definitely learned from that game and the times before when I didn't have my stuff."
He didn't have to worry much about his stuff on Sunday. Melvin said Manaea's velocity wasn't in tip-top shape, but everything else was working.
The rookie threw first-pitch strikes to 18 of the 27 batters he faced, pinpointing his fastball on the black of the plate with regularity.
"Being able to locate my fastball like that was just huge for me," he said.
Even better? He worked in some offspeed offerings early in the count, meaning the Astros' free-swinging sluggers couldn't sit on his flatter fastballs.
"Throwing a changeup and sliders for strikes, showing them on the first pitch and getting ahead of their aggressive hitters was key," Manaea noted.
He was ultimately pulled after 106 pitches, 72 of them strikes, walking none while striking out six. Manaea was the first Oakland rookie to notch seven scoreless frames without a walk since Dan Straily on May 21, 2013.
It required steep composure, especially for a first-year hurler. He was locked in a pitchers' duel with reigning American League Cy Young Award winner Dallas Keuchel, and his team committed three errors while he was on the mound.
"It was pretty difficult, because it's extra outs for them, but I trust my teammates," Manaea said. "They're going to falter at times, just like I do. It's going to happen. You battle through it and I totally have faith in them next time."
Manaea has made solid progress since his MLB debut against Houston on April 29. In that outing, he allowed four runs and lasted just five innings.
Now he seems in complete control, walking just five batters in his last four outings while exiting with a lead in four of his last six starts.
"He's pitching great," Melvin said. "He keeps getting better and better and it seems like he pitches with more confidence. ... But today, it looked like he had some experience and really pitched more so than he has in the past."
Manaea said he's not a wily veteran just yet, while agreeing that some bumpy outings have aided his development as a rookie.
"Having the ups and downs and coming out every day trying to get better, it's been a long process, but it's been fun and I'm happy with how things have been progressing."