"I've seen her sing on YouTube," Knapp said following the Phillies' 4-3 victory over the Reds. "She's famous. I recognized her right away."
VanHoose, who was born blind, belted out the final words of the anthem, then, on cue, two F-16 Fighting Falcons rocketed over the ballpark.
The crowd roared.
"That was awesome," Knapp said. "I was getting goosebumps the whole time. I mean, it was Opening Day. It's kind of hard to describe the feeling when you're standing on the line. It was kind of surreal."
"I had goosebumps the whole time," Stassi echoed. "It was a special moment."
Knapp and Stassi took different paths to the big leagues. The Phillies selected Knapp in the second round of the 2013 Draft. He has been one of the Phils' top prospects ever since, so he seemed destined for this moment. But Knapp still has a tremendous appreciation for the accomplishment. His father, Mike Knapp, played 11 seasons in the Minor Leagues, but never reached the Majors.
The Phillies selected Stassi in the 33rd round of the 2011 Draft. The fact Stassi even entered the conversation to make the 25-man roster before camp opened in February was a surprise. Then he made the team.
Stassi's emotional reaction to the news Thursday in Clearwater, Fla., went viral. Anybody with a heart could relate to a long shot reaching his dream, particularly in a Rocky-obsessed city like Philly.
It has been a whirlwind ever since.
"It's been unbelievable," Stassi said. "The feedback I've been getting from Phillies fans has been incredible. People have messaged me and said how much of an inspiration I am and how they're going to tell their high school team my story, stuff like that.
"Wow. I never expected any of that."
Stassi and Knapp having been soaking up the big league experience as much as possible. Triple-A Lehigh Valley flies commercial and players often find themselves stuck in the middle seat next to strangers. In-flight meal? Sure, if it's available and they want to pay for it.
The Phillies chartered flights from Clearwater to Philadelphia on Friday, and from Philadelphia to Cincinnati on Sunday.
Security lines? Nope.
"That's by far the coolest thing," Knapp said.
Middle seat? Big leaguers get a row to themselves.
Hungry? What are you in the mood for?
"The food on the plane, I've been crushing a lot of that," Stassi said. "The first day, I ate like eight plates of sushi before the flight even took off. It's been crazy. It makes all those long bus rides in the Minor Leagues worth it."
"It sounds dumb, but everything is big league," Knapp said. "Everything is taken care of."
Knapp, who had family in town, said he woke up earlier than expected Monday.
"When you're young, you look forward to certain days, like your birthday and Christmas," he said. "Today was that day for me. My dad and I were both at breakfast, and we were both like, 'When are you going to the field?' It's 9 o'clock, but it's like, 'Right now, let's go.'"
The first bus left for the ballpark at 10:45 a.m. ET. Knapp was one of the first people on it.
After the game, Knapp said his favorite memory was seeing Stassi pinch-hit in the eighth inning. Stassi, who had 17 family members and friends in the stands, walked.
"Standing in the on-deck circle was a little more nerve-wracking than when I was in the box," Stassi said. "Sammy [third-base coach Juan Samuel] actually gave me the 3-0 green light and my heart started kind of beating. The pitch was a little lower than I like it, so I didn't swing."
"We're kind of in the same position, we both haven't been here before," Knapp said. "To see him get that experience is pretty cool. And then we won."