It turned out to be an up-and-down outing for the 24-year-old, who had not pitched in a game in almost two years. But a big league promotion is a huge deal for a kid who missed the entire 2019 season recovering from Tommy John surgery.
With the Nats down 3-1, the Nats' 2017 first-rounder took on the Mets' speedy outfielder Billy Hamilton to lead off the bottom of the fifth. He got Hamilton to strike out swinging on a slider.
"I was 100 percent nervous for the first one," Romero said on a postgame Zoom video call. "But after the first few throws I kind of settled in. Right off the grip, yeah for sure, definitely nervous."
He then allowed back-to-back singles to Michael Conforto and Pete Alonso. After striking out the dangerous Dominic Smith, Romero walked AndrÃ©s GimÃ©nez to load the bases. With two outs, the southpaw from West Columbia, Texas, had a chance to get out of the inning. He managed to get to 0-2 against Mets catcher TomÃ¡s Nido before the catcher was able to turn on a Romero changeup and launch a grand slam. The Mets led 7-1.
"I wasn't too worried about it," Romero said about allowing the grand slam. "I felt good on the mound. Things happen. So, I didn't really think about it too much and just tried to focus about the next pitch.
"I wanted to get the changeup down like I did the first one I threw to him, but kind of just got under it, pushed it up there, gave him a good pitch to hit."
Romero returned to begin the sixth inning, recording a pair of walks but also striking out J.D. Davis and Conforto.
He finished 1 2/3 innings, allowing four runs on three hits with three walks and striking out four batters. Romero tossed 43 pitches, 24 for strikes, mixing a four-seam fastball with his slider and a changeup.
"I thought with all the lefties coming up that was a good spot for Romero," manager Davey Martinez said in his postgame Zoom video call. "I thought he threw the ball good. His first outing in the big leagues, got the early strikeout, and then the walks.
"I told him, 'The walks, when you are up here you walk one or two guys. These guys can all hit. Just throw strikes. That's all I ask, is that you throw strikes.' He was nervous, but like I said, when he did throw strikes he had a lot of swings and misses. It was nice. He's got good stuff."
Martinez and pitching coach Paul Menhart came out to the mound during Romero's outing.
"I joked around with him on the mound a little bit," Martinez said. "I can't tell you what I said. That's in the circle. But I got him to laugh a little bit."
Menhart reminded Romero he was on the big club for a reason, because he has the stuff to get guys out at the big league level.
"Paul just kind of came out there and told me to trust my stuff, stick with it, just kind of get it back together, just do what I do best," Romero said.
This week Romero was called up to the taxi squad in case the Nats needed a left-handed pitcher. Sam Freeman went down with a left flexor mass strain Wednesday night. Sean Doolittle has struggled with his velocity to start the season. The Nats put him on the 10-day injured list with right knee fatigue.
Martinez recounted the moment he told Romero the big news before today's finale.
"It was awesome," Martinez said. "I brought him up to the office right before the game. One, he had a pair of earrings in and I just told him, first and foremost, the earrings got to go. Secondly, congratulations. You are going to pitch for us. You could see it in his face he was elated. I told him 'Hey, be ready today because you'll probably end up getting in the game somehow. But congratulations. I know you can do this, and just go out there and have fun.'"
Romero confirmed having to take off the earrings.
"He just pretty much called me in and he said, 'First things first, take out your earrings,'" Romero said, smiling. "I didn't even realize I still had them in. After that he kind of told me what was going on for today.
"I have just been trusting the process. Sticking with what they've told me, doing everything they've told me. Just trying to stay healthy just in case they needed me."
Romero's last game was Aug. 16, 2018, in a start for low Single-A Hagerstown against the Lexington Legends. He tossed two shutout innings, allowing one hit, no walks and three strikeouts. He did not pitch in one game in 2019, and then minor league baseball was canceled for this season. But then he got the call telling him that he would be placed on the Nats' 60-man player pool. Martinez and the staff noticed Romero's progression the last month in Fredericksburg. They placed him on their first five-man taxi squad earlier this week.
"We were watching him progress," Martinez said. "We were watching him down in Fredericksburg and he was a guy that was throwing strikes, and that's important here. Throw a lot of strikes, he's always in the strike zone. We feel like he's got a lot of swing-and-miss stuff, and we need a left-handed pitcher. Right now, he's the only lefty we got with Doolittle going down. We thought it would be a perfect opportunity to get him up here and see what he can do."
Romero remembered what it felt like the first time he picked up a baseball again after having Tommy John surgery.
"I am pretty positive that all my first five throws went straight into the ground," Romero said. "Yips. I thought I had the yips already."
Throughout all those days and months he rehabbed, hoping for a chance to pitch again, Romero never stopped believing he could do it or that all that hard work was wasted.
"I didn't ever think that the day wouldn't come, but I definitely knew I was putting myself in a tough position," Romero said. "I tried to put that all behind me and do what they would tell me to do and keep working."
One guy who can relate to Romero's emotions Thursday was today's starter, Voth. He also made his major league debut at Citi Field, a rocky 7-4 loss to the Mets on July 14, 2018.
"It's got to be a good feeling for him," Voth said during a postgame Zoom video call. "I made my debut in this stadium, just kind of getting it out of the way. Sometimes they are good, sometimes they are bad, but just knowing you made your debut, you're a big league pitcher. You can kind of throw this aside, and whatever opportunities you have in the future you know that you're a big leaguer and you just need to prove yourself now."
And that's the takeaway. Despite the rollercoaster of a first day, the biggest fact of the matter is that Romero is now officially a major league pitcher, which is a dream come true.
"I didn't really think that I have processed it yet," Romero said. "I can't wait to get back on the mound again for whenever they need me, and I'm excited."