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OAKLAND -- Once Adam Oller achieved a lifelong dream of pitching in the big leagues after making his debut back in April, the next box to check off on his list of goals was first Major League win.

It required a few months and various trips up and down from Triple-A Las Vegas, but Oller finally reached that milestone on Monday, earning the victory after a solid outing of five-plus innings against the Astros.

“It’s unreal,” Oller said of picking up his first big league win. “It only took four months, but we got it. It goes back to all the stuff in between. All the ups and downs through the Minor Leagues. The long hours in the offseason working. To finally get to this point, it goes to trusting yourself.”

Trusting in himself is something Oller often struggled with most of his career. A 20th-round selection by the Pirates in the 2016 MLB Draft, Oller was released just two years later and soon embarked on a turbulent journey that included stops in independent ball and winter ball in Australia just to keep his dream alive.

Even after getting traded over from the Mets this spring as part of the return for Chris Bassitt and making Oakland’s Opening Day roster, Oller still struggled with convincing himself that he belonged at this level. 

“That’s something I’ve dealt with in the past -- not being confident enough in myself,” Oller said. “Thinking I don’t deserve to be here. I think everybody goes through that.”

Following his most recent demotion to the Minor Leagues, however, that mindset changed.

Optioned to Triple-A on June 30, Oller was given a clear message from the A’s coaching staff: If he wants to have success at this level, he needs to focus on throwing his fastball more and show he can do so effectively. Sure enough, Oller recalled his first start back with Las Vegas after that. He threw fastballs for 47 of his 57 pitches and allowed only one run.

“At the time, I was upset. Looking back, I’m glad they did that,” Oller said. “It forced me to get out of my comfort zone and trust myself, and I did. It ended up working out. It led to me being where I’m at now to where I trust what I’m throwing and anyone behind the plate.”

The A’s have cycled through several different pitchers in search of filling their fifth-starter slot in the rotation. With Oller's sharp command of his fastball, which sat around 95-96 mph on Monday night, the 27-year-old rookie has likely earned a longer look in the big leagues this time around. Next up on that list of goals: Establish himself as a big leaguer.

“Getting traded over in a big trade, there are expectations put on you,” Oller said. “I wasn’t fulfilling any of those expectations. There were a lot of moments in the first half of the season where I had to take a look in the mirror and look at myself and decide what I wanted to be. I told myself that the second half was a new start and tried to put myself in the best situation to help myself and help the team that believes in me.”

For now, Oller gets a few days to enjoy a first win that was years in the making. He had his game ball from Monday night authenticated and stored in his locker inside the A’s clubhouse. 

Asked where that ball will go next, Oller said, “My parents. The stuff they’ve done and sacrificed for me to get where I’m at, truly I wouldn’t be here without them. The amount of times in the Minor Leagues I called my parents broke, they would do anything for me. Anything I have goes to them.”