Frankie Montas was virtually unhittable on June 20 of last year, allowing the Tampa Bay Rays just four hits and one run over eight innings. He struck out nine, walked none.

The A’s right-hander was at the peak of his powers, flashing a four-pitch mix featuring a new and devastating splitfinger developed earlier in the year. It fell in line with an excellent start to the season, when he was starting to realize vast potential.

His next outing came against air. Montas pitched then and every turn in the rotation after came for months in exile while serving an 80-game unpaid suspension for a positive PED test. He returned to his home in Arizona upset but hellbent on continuing what he started.

“When I left I was determined to keep working hard,” Montas said. “I kept the same routine, throwing every five days like I was in the rotation. It was a long time away and it was frustrating for sure, but it was important to make my return a good one. I felt like I needed to help the team in any way I could after being away so long.”

Montas got one shot at it, on Sept. 25 against the host L.A. Angels. He retained previous form in a shockingly similar outing to that June 20 start, allowing one run on four hits over six innings this time. He had six strikeouts and two walks in his one and only return to action that season.

While the A’s were upset losing Montas to an avoidable setback, manager Bob Melvin was pleased with his return.

“The most impressive thing to me last year was not what he did in the first half,” Melvin said. “It was when he came back and had to pitch in a pennant chance. That meant that he worked very hard in his downtime to come back and give us what we gave us that day.”

The A’s believe Montas can provide that type of performance on a regular basis this season. While spring outings don’t mean much, he hasn’t allowed a hit in three efficient innings thus far.

His threw two of them Monday, and struck out Jason Hayward on this nasty splitter:

What a splitter from Frankie Montas pic.twitter.com/bSpjzncGn7 — Alex Fast (@AlexFast8) March 3, 2020

That pitch gets a ton of credit for last season’s success, as it should. Montas exchanged a just okay changeup for an awesome splitfinger he developed pretty fast.

“I started messing with it in spring training last year, and I felt like it started working the first day I threw it,” Montas said. “I thought quickly that this was something I could add to my repertoire. There was work to be done finding the right release point, but I really thought it could help my game.”

The appropriately-hyped addition was well documented last spring, and it served Montas well over 16 starts. He threw it 18.2 percent of the time, the lowest amount of an arsenal that also includes a sinker, slider and four-seam fastball, but was it ever effective.

Opponents hit just .160 against it and their 80.2-mph exit velocity was the lowest of any of his pitches, per Statcast. Hitters swung and missed at the splitter 40.3 percent of the time. It paired with the slider as an effective put-away pitch. With two, it made Montas hard to predict. Pairing all that with a high-90s fastball has sent optimism sky high for what he can do over a full season.

It’s also safe to say that adding the splitter increased his overall effectiveness, but we can’t forget something Montas is most proud of during a transformation from bullpen arm in 2017 to frontline starter.

He has learned how to pitch. While some point straight at the splitfinger, Montas also considers the year before it was developed as a major growth period. He expanded his pitch mix and worked hard to improve command in 2018, after a year spent in the bullpen and made some strides that got things really rolling towards last season

“2018 was a big year for me,” Montas said. “I talked to a lot of veterans that year because I’m a guy always asking around about how to pitch. I’m not afraid to ask questions of guys who have been around longer about how to improve my game and how to throw the right pitch at the right time.”

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He tries to absorb information from the coaching staff and his peers. He attached himself to Mike Fiers especially and Sean Manaea, trying to take whatever he could from guys who have been around the block.

“Those guys have been good in the big leagues and, in order to follow those two guys, you need to up your game. You have to be at their level and I’m working hard to be there every start. … I have great respect for how Jesus [Luzardo] and A.J. [Puk] work as well and feel like I can learn something from them even though they’re younger than me. I watch those guys throw bullpens and try to take something from that. I try to learn from everybody here.”

NBC Sports Bay Area reporter Dalton Johnson contributed to this report.