During last year's contest, White landed his final run of the night to snatch the victory from front-runner Gagnon, who was gunning for a record fourth-consecutive Skateboard Vert gold medal. Gagnon finished with the silver.
"I was kind of expecting him not to skate this year," Gagnon, 32, told ESPN.com. "I know Shaun's been in New York and I know he doesn't have a ramp to skate right now. I definitely had a feeling that [X Games] didn't seem like his main priority, and he's not the kind of guy to show up and wing it."
"He had a great snowboard season," Gagnon added, "and now maybe he just wants to take it easy, enjoy life."
Earlier this year, White won three gold medals in snowboarding at Winter X Games, including a perfect SuperPipe score in Aspen, during which he pulled off back-to-back double cork 1260s, and then won two gold medals in Tignes, France, in SuperPipe and Slopestyle. White's Skate Vert contest history dates back to 2003, with gold medals in 2007 and 2011.
With or without White in this summer's X Games, Gagnon says his game plan will remain the same.
"I'm just focused on what I need to do to be on top of my own skateboarding. And right now, I feel great," he said. "I'm skating every day. I've got my tricks down. I'm just doing what I've been doing for the past 15 years."
Bucky Lasek, last year's bronze medalist and a top Skateboard Vert competitor since 1997, said that White's absence "doesn't change things. Just because one guy doesn't show up doesn't mean the contest is going to be easier. Every skater still has to skate at the very top of his own personal level."
Even with White sitting this one out, the highest levels of the discipline's veteran contingent will be put to the test.
Mitchie Brusco, 15, is in the lineup, with a decade of halfpipe riding under his belt. Fans will also look to highly progressive skateboarding from Brazil's Pedro Barros, 17, and Southern California prodigy Alex Perelson, 21, who's been called the new face of Vert.
Tune into the Skateboard Vert finals at X Games LA on Saturday, June 30 starting at 9 p.m. on ESPN. Check out the full tune-in schedule here.