He has beaten the players seeded third through eighth in the regional tournament, including No. 6 seed and teammate Will Stevens. He hasn't faced No. 9 seed Jeff Ricker of Danville.
Despite being a middle-school student, Arndt is tournament-tested. He won his first trophy on his eighth birthday and holds a city record in Watertown, S.D., for wins in a one-month tournament.
He finished second in the 14-and-under state tournament in Virginia in 2001 when he was 11. He said he expects the regional tournament to be similar to playing in Virginia's state tournament.
"It's going to be a lot harder playing against these older people," Arndt said. "I'll probably be a little bit nervous."
When Arndt first got to Garrard, Mike Stevens knew he had the game skills to be a top player. But he hadn't yet seen how he would handle pressure situations.
The coach's son, Will Stevens, had been playing No. 1 singles for Garrard for several years. The team played challenge matches to set the lineup, and Arndt and Stevens each defeated the other.
Stevens still started the season at No. 1, but Arndt moved up to that spot in the third match.
"I played Will the first time and I beat him the very first match," Arndt said. "When we played a couple of our first matches, he was playing No. 1. I was wondering why because I was thinking, 'I beat him, but I'm still playing No. 2.'"
"His style is more fluid than Will's, but I didn't know if that would translate into being able to play well, because you have to think and be mature with it too," Mike Stevens said. "At first, it was kind of nip and tuck between he and Will. Over time, as Phillip got more settled into playing at the high school level, that was a big thing for him."
In Virginia, students must be high school age to play for high school teams. Arndt didn't face that restriction when he got to Garrard, and he admitted it took him a little bit of time to adjust to playing with older teammates.
However, he also said he's faced his fair share of good-natured ribbing.
"I think I kind of fit in, but they're always making jokes about me that I'm too young," Arndt said. "They say things like, 'Only an eighth-grader would do something like that.'"
But to an outsider, Arndt wouldn't look like a typical middle-schooler. With a deep voice, he comes across as older than he is, and Stevens said he's also bigger physically than most others his age.
"To talk to him and look at him, you'd think he was older than what he is," Stevens said. "The boys were excited about him being there. I think he was pretty much accepted from day one."
Arndt has taken advantage of the knowledge his teammates have accrued over the years, asking his teammates for advice on how to play certain players.
"I was just always asking questions like, 'Who is this guy?' or 'How does he play?'" Arndt said. "They kind of helped me out throughout this season."
Now, it's down to his final lesson. Mike Stevens said he knows Arndt has the skills, but it will all depend on how he handles the regional setup.
"I think probably that would be the big thing," Stevens said. "I think that will be the thing for him as to whether he can be mature enough in his thinking to not panic."