BOSTON -- When Drew Rasmussen joined the Rays’ bullpen in Seattle on June 19, the right-hander looked back on the circumstances that led him to, as he said, “where I belong.”

Drafted by the Rays 31st overall in 2017. Unsigned, as he needed a second Tommy John surgery. Selected by the Brewers in the sixth round a year later. Sent to the Minors as a starter in ‘19. Moved to the bullpen at Milwaukee’s alternate training site last year. And, finally, traded to the Rays on May 21 of this year, along with high-leverage reliever J.P. Feyereisen in exchange for popular shortstop Willy Adames.

Even then, it took a little more time for Rasmussen to get back to where he belonged.

“The Rays knew what they were getting out of the situation,” pitcher Chris Archer said, “and it wasn't just two relievers.”

Mindful of his previous surgeries, the Rays eased Rasmussen into their system by assigning him to Triple-A Durham. He joined their bullpen for two days in Seattle, then got sent back to the Minors to make room for former top prospect and current rookie sensation Wander Franco. Rasmussen returned to the Rays’ bullpen three days later and carved out a role as a multi-inning reliever.

A month ago, he moved into the role Tampa Bay’s front office envisioned for him more than four years earlier: part of the Rays’ starting staff. On Tuesday night, he earned his first win as a starter by holding the Red Sox to one run over five innings in the Rays’ 12-7 victory at Fenway Park.

“First big boy win,” Rasmussen said afterward, smiling. “Get to go five and we win, that's pretty cool.”

Rasmussen is thriving in this role, posting a 1.64 ERA in 22 innings over five starts. The Rays have been careful with his workload, only allowing him to pitch four or five innings each time out, but Rasmussen has made the most of his innings by working efficiently, adding to his arsenal and pitching with quiet confidence that should serve him well down the stretch.

“I think what he's done for this team is exponential,” catcher Mike Zunino said. “Just the way he's throwing the ball, he's a game-changer when you're talking about who you're going to line up in a playoff series, and I think he’s showing that.”

Since ace Tyler Glasnow went down with an elbow injury that required Tommy John surgery, many observers have wondered how the Rays might line up their starters for a series in October. It’s perhaps the biggest question facing the American League East leaders while they close in on their third straight trip to the postseason, as they have MLB’s highest-scoring lineup and the AL’s most effective bullpen.

The Rays have plenty of options, even if they’re younger (like hard-throwing Shane McClanahan) and less proven (like 21-year-old Luis Patiño) than last year’s starting trio of Glasnow, Charlie Morton and Blake Snell. Their deep bullpen would be able to go all-out in short series with built-in off-days, too.

But as Zunino said, the emergence of Rasmussen adds another layer to the Rays’ potential postseason pitching staff.

“He might actually have as good of fastball command as anybody we have on our team,” pitching coach Kyle Snyder said, also crediting Zunino and Francisco Mejía for encouraging Rasmussen to attack the zone. “He’s a tremendous talent. He’s gone through a lot in his career with the two arm injuries, but I feel really good about where his delivery is and I know he feels good about where he stands physically.”

Tampa Bay discussed the idea of starting shortly after acquiring Rasmussen, but initially used the 26-year-old as a multi-inning relief weapon, like Collin McHugh. But as Rays officials considered how to move forward without Glasnow, they reconvened with Rasmussen about his personal aspirations and how those goals aligned with their view of him as a long-term starter.

They’ve had to be cautious, not wanting to overload his arm or burn through innings too early in the season. Since making his first true start at Fenway Park on Aug. 12, he’s maxed out at five innings, which may be his limit the rest of the way.

But as a “sprint-work starter,” as Snyder called him, Rasmussen can let his high-octane fastball fly and lean on a slider that’s produced a .187 opponents’ wOBA this season. He’ll likely refine his curveball and changeup to become a four-pitch starter next season, but his stuff’s already a big part of the intrigue.

Consider how his four-seam fastball metrics this season compare to the elite stuff of Glasnow, per Statcast.

Rasmussen: 97.2 mph, 2,445 rpm average spin rate, 11.4 inches of drop, 27% whiff rate, .303 xwOBA

Glasnow: 97 mph, 2,424 rpm average spin rate, 11.9 inches of drop, 27.8% whiff rate, .300 xwOBA

Of the 228 pitchers who have thrown at least 200 sliders this season, Rasmussen and Glasnow are two of only 16 to produce at least five extra inches of downward action over other sliders at their velocity. Sort that group of 16 by average fastball velocity, and you’ll find that the top three are Rays: Glasnow, reliever Pete Fairbanks and, atop the list, Rasmussen.

And he’s not afraid to challenge hitters with it, as the Rays encourage their pitchers to do. In his last five starts, Rasmussen has thrown 67 percent of his pitches for strikes while averaging a mere 14.05 pitches per inning.

“He just gets it and throws it. He pumps a lot of strikes. It’s allowing the defense to make plays behind him,” manager Kevin Cash said. “When he needs a strikeout, you can tell he's got a knack for dialing it up and turning that 95-6 [mph] into 98 or breaking off a little bit nastier slider.”

He’s got the stuff. He’s got the opportunity. Feels like this is where he belongs, right?

“I do think in terms of stretching it out and building up a pitch count, building up innings and the ability to sit down and get back up again, things have gone pretty well,” Rasmussen said earlier this week. “Not perfect. You're probably never going to hear me say it was perfect. So I'm happy with how things have gone, but the job's not done yet.

“We still have another month in this season -- and hopefully much more than that.”