Being the runner-up has never felt so good.

As the globe celebrated Desiree Linden’s historic Boston Marathon win on Monday — and the day’s torrential downpours washed out world-class athletes like Mamitu Daska of Ethiopia — an unknown Arizona nurse with no sponsors, who wasn’t even listed among the elite women’s field, quietly crossed the finish line in second place and took the $75,000 prize.

“I’m still processing it all. This has all been such a whirlwind,” Sarah Callister Sellers, 26, told Moneyish. This was only her second marathon, and she finished four minutes behind Linden in 2:44:04 — the first time two Americans have finished first and second in Boston since 1979.

Sellers was a track star while studying at Weber State University in her native Utah, where she won every one of her 5,000-meter and 10,000-meter races, her coach Paul Pilkington told Moneyish. (Her university notes she also kept up a 4.0 GPA in nursing.) But she stopped running for a couple of years after breaking her foot her junior year, and while going to grad school to become a nurse anesthetist.

“She has this ability to just go out and hammer and run incredibly fast,” said Pilkington, who has continued to train her. “She’s an excellent racer. She never lost a track conference or championship race.”

Sellers won her marathon debut in Huntsville, Utah last September — setting a course record with her 2:44:27 finish in the process — and qualified to run this year’s Boston Marathon. So Pilkington drew up a training plan in which she pounded out between 80 and 85 miles a week — which is actually low compared to the 100-plus miles many elite professional athletes put in. She squeezed in runs before and after her 12-hour nursing shifts, which saw her hitting the road as early as 4 a.m. or as late as 8 p.m.

Pilkington said that Sellers often trained with Olympic-caliber runners while she was at Weber, so her running with the elites isn’t unusual. “Sarah’s not intimidated. In her mind, she believes that she should be able to race with any of them,” he said. “She’s very savvy and smart and tough, and those conditions yesterday played into her grittiness.”

ALSO READ: 6 things Boston Marathon winner Desiree Linden can teach us about running the world

Sellers entered Monday’s race hoping to make the top 10 and qualify for the U.S. Olympic Marathon Trials two years from now. Unlike many of the elite runners who are invited to race for free, and who have sponsorships to cover their travel, accommodations, meals and gear, Sellers paid the $180 race entry fee and coughed up about $1,500 for airfare and a hotel outside of Boston for herself and her husband.

She started off running slower than her usual sub six-minute-mile pace because of the rain. “Turn your shower on cold, and put it facing you with the full pressure blasting you in the face — that’s what yesterday felt like,” Sellers said. “There were points during the middle of the race where, if it weren’t for your pride, you would want to throw in the towel. But there are keywords that I like to think of during races, so early on I kept thinking ‘composure,’ and then for the last six miles it was ‘confidence.’”

And as she hoofed the 26.2 miles from Hopkinton to Boston, Pilkington — who was following her via the online race tracker — noticed his student was picking off the elite runners one by one. “When I saw her cross in second, I thought for a minute that they had missed someone finishing,” he said. “I kept hitting refresh on the results to make sure it was true.”

Sellers was so focused on putting one foot in front of the other that she didn’t actually comprehend that she was passing running legends like 2017 New York City Marathon winner Shalane Flanagan and U.S. Olympian Molly Huddle.

ALSO READ: 7 life lessons from New York City Marathon winner Shalane Flanagan

“It was a little bit surreal when I was passing some of the bigger names in the race … Shalane Flanagan and Molly Huddle are two of the most accomplished women in the field. They’re incredible athletes. And I don’t think I’ll ever fully process passing them,” she said. “You know, when you have ‘marathon brain’ you’re not really thinking clearly. I assumed there were still quite a few women ahead of me.”

In fact, Sellers didn’t believe the race marshal who congratulated her for getting second. “I found my husband at the finish line and asked him what place I was really in, because I thought it was a joke,” she said.

Now Pilkington says that Sellers’ life could completely change. At least one major running shoe company has already approached them for a potential sponsorship. (He wouldn’t say which, but Sellers was wearing $99.99 New Balance 1400v5s during the race.) And after taking second at Boston, one of the most iconic marathons in the sport, many big-city marathons will now roll out the red carpet to invite her and cover her entry fees and expenses.

Sarah Sellers — seen at Mile 24 — finished the 2018 Boston Marathon in second place at 2:44:04. (Scott Eisen/Getty Images)

And then there’s that $75,000 prize, which Sellers says that she and her husband will probably put toward their student loans. “We’re going to try and be responsible,” she said. “But this does justify continuing to pursue this hobby of mine, and not feel like I’m overspending when I buy new running shoes or travel to a race.” (That is, if she even has to pay for those anymore.)

But for now, she’s soaking up her newfound celebrity, which has included someone creating a Wikipedia page for her; her Google search hits going from practically nothing to 6.8 million results overnight; and getting to meet her running heroes at the winners’ celebration on Monday.

“I met Shalane Flanagan at the award ceremony. She was very gracious and kind, and she set the precedent for American distance running by winning New York last fall. That was super iconic. So it was great to meet her, and she was just so kind and down to Earth,” Sellers said.

Otherwise, she plans to go back to work on Thursday. “I don’t think much will change on a day-to-day basis, just because I love working, and I think my work gives me added confidence,” she said. “I’m going to return to the routine that I had going, and just keep moving forward, setting big goals and working toward them.”

She says she’ll probably run a fall marathon such as Chicago or New York, and keep training for the Olympic Marathon Trials two years from now. But whatever happens next, she’ll be a marathon star forever.

“I got second at the Boston Marathon, and that is never going to un-happen,” she said. “That is kind of crazy.”