Like Nelson, who attended Logan High, he began the season in relative obscurity while playing behind more high-profile teammates.
Last week, however, Falslev jumped into the spotlight.
During TCU's 38-28 win over BYU, he caught a team-high five passes and became the first Cougar since 2006 to return a punt for a touchdown.
BYU receivers coach Ben Cahoon isn't surprised by Falslev's production, even though he's only 5-foot-8 and weighs 185 pounds.
"His strength is his toughness," Cahoon said. "... His toughness and courage allow him to go over the middle and make those difficult grabs."
Cahoon knows a little something about being an undersized-but-effective receiver.
Despite standing 5-foot-9 and weighing 190 pounds, Cahoon was a 10-time Canadian Football League All-Star during his career with the Montreal Alouettes.
"I think JD has a little short-man syndrome in him," Cahoon said. "And that serves him well on the football field. He plays with a chip on his shoulder. He's fearless. We need more of that around here."
Of course, everybody talked about the same thing toughness, no fear when Nelson emerged as BYU's starting quarterback.
"It's kind of funny," Nelson said. "Growing up in northern Utah true or not the mindset is we've got tough, physical football players at every position.
"We let everybody else look pretty and be fancy. But we're like, 'Don't worry about how it looks to others on the outside. We're going to get after it.' "
Falslev starred at Sky View but, because of his size, he didn't generate much interest among college recruiters.
A handful of Ivy League schools wanted Falslev, who considered the possibility until he realized those institutions only awarded academic scholarships.
"Don't get me wrong, that's a huge thing a great thing," Falslev said. "But it did discourage me a little bit."
When neither Utah nor Utah State showed much interest, Falslev focused on BYU.
He had attended youth football camps in Provo, developed a "great relationship" with the coaches and hoped it would lead to a scholarship.
Instead, Falslev ended up as a walk-on.
Falslev's immediate effect at BYU came as a punt returner and, this season, he averages 11.2 yards on 13 returns.
Lately, however, Falslev has also emerged as a change-of-pace, possession-type receiver. He's caught 18 passes for 142 yards and a touchdown.
"I enjoy throwing to JD because he creates a lot of separation," Nelson said. "Obviously he's not big. But he's fast and his quick feet allow him to create such separation that it opens up big windows for the quarterback."
Falslev enjoys his dual role at BYU, especially because so many doubted he'd ever be a major college receiver.
"I don't know if I had to prove myself," he said. "I just knew I didn't want be just a return specialist. I wanted to be a receiver, too, and I feel like I'm gaining momentum" in reaching that goal.
"If you stay humble and hungry," he said, "you can do things other people don't think you can do."
The JD Falslev file
Position • Receiver, kick returner
Height • 5-8
Weight • 184
Class • Sophomore
Hometown • Logan
High School • Sky View (2009)
Career • All-State at Sky View.
Also lettered in baseball and basketball
Walked on at BYU but now on scholarship
Lettered last season as a freshman after playing in all 13 games
Averaged 9.1 yards on 15 punt returns
Returned a punt 43 yards against UTEP in the New Mexico Bowl
This season has caught 18 passes for 142 yards and a touchdown
Averaging 11.2 yards on 13 punt returns
Returned a punt 67 yards for a touchdown against TCU.