Three of the most dreaded letters in sports are A-C-L, shorthand for the knee injury — a torn anterior cruciate ligament — that waylays scores of athletes, nearly always ending their season.

The Vikings have lost a first-round draft pick to a torn ACL two straight seasons, with Mike Hughes succumbing this month to the same injury that befell Dalvin Cook last year.

But over at the University of Minnesota, there's an ACL story with a happier ending, at least for now.

Gophers soccer captain Emily Peterson suffered a torn ACL on March 13, during team's spring break trip to Italy. A day spent touring the Colosseum in Rome gave way to agony for Peterson, a senior from Prior Lake whose right knee buckled during an exhibition game.

"At that point, I was like, 'My senior season's done,' " Peterson said. She had surgery March 26.

But by Sept. 20, she was back playing in games for the Gophers again. Do the math, and the comeback happened in less than six months.

Doctors don't recommend this course. Iowa had a football player in 2017 who returned from a torn ACL in 5 ½ months. Brandon Snyder celebrated his return with an 89-yard interception return. That same game, Snyder retore his ACL, one of four major ligaments that stabilize the knee.

"Realistically, that [rehab] takes a lot longer than six months," said Dr. John Wilckens, a Johns Hopkins orthopedist who has done more than 1,200 knee surgeries over 35 years. "I certainly don't want to penalize anybody for healing fast and working hard, but [Peterson's] probably on the outside of normal."

Gophers coach Stefanie Golan put it another way: "Petey's just an incredible human."

"When we were recruiting her," Golan said, "there were a lot of people who thought something was wrong with us because there's no way that Emily Peterson was supposed to be able to play at this level."

After appearing in just one match as a freshman, Peterson was a key reserve in 2016 on the Gophers' Big Ten title team. She rarely left the field last season, anchoring the defense from the center back position. Friday, two days before the team's Big Ten quarterfinal Sunday at Rutgers, Peterson was honored as the team's sportsmanship award winner.

"She reads the game fantastically well," Golan said. "She's really difficult to beat, organizes the back line, battles things in the air. I mean, she's a fighter."

When most Minnesotans think of "Peterson and ACL" they think of Adrian, the former Vikings running back who tore his ACL and MCL (medial collateral ligament) on Christmas Eve 2011 and returned to win 2012 MVP honors.

Emily Peterson didn't have quite as much knee damage. Hers was a "clean tear" of the ACL, with no other ligament or cartilage damage. She had little swelling and surprisingly little pain. A surgeon replaced the ligament with a graft from Peterson's patella tendon. He predicted an eight-month recovery.

"Emily's work ethic was outstanding, unlike anything I've ever seen before," said Gophers athletic trainer Sarah Wambheim. "At her three-month check-in, the physician was already saying, 'I think we can talk about you coming back months earlier than expected.' "

Peterson was ecstatic. Her parents, Paula and Kent? Not so much. Their oldest daughter, Megan, had twice torn her ACL during high school, ending her college soccer hopes. And Paula had suffered her own torn ACL, skiing in Big Sky, Mont.

"Of course, Kent and I were scared when Emily started talking about coming back this season," Paula said. "Why? Why not redshirt? But we quickly discovered it was best to let Emily do her own thing."

The risk of retearing an ACL gradually decreases after surgery. In 1997, Jerry Rice tore his ACL in Week 1 and returned by Week 15, though he later admitted that was far too soon.

Wilckens said more athletes rushed their returns from ACL surgeries until a philosophical shift arrived more than a decade ago.

"We began a critical look at the data and discovered there's a fair amount of people reinjuring their ACLs," Wilckens said. "So as a profession, we took a step back and said, 'We need to rehab these people a little bit longer.' "

But Peterson was determined to finish her college career with her senior class.

"I'm not planning on playing after [college], so I was like, 'I don't really have much to lose,' " she said. "Obviously, the doctor warned me that it's not the best for my knee down the road. But I was willing to take the risk."

Paula said her mind eased when she viewed the step-by-step video of Emily's rehab, a specialized program devised by Gophers strength coach Corey Petersen.

"She did not miss a day of rehab," Paula said. "And now she's stronger and faster than she ever has been."

Peterson played limited minutes when she first returned from knee surgery but is back to playing full games again. So the Gophers have their captain back at full strength, just in time for their must-win match Sunday.