PALO ALTO, Calif. -- The Tennessee Volunteers will have someone playing for the NCAA singles championship.

As for who that representative will be, sophomores Rhyne Williams and Tennys Sandgren will decide that issue when they meet in Sunday's semifinal match at the Taube Family Tennis Center.

Williams and Sandgren earned straight-set victories for the fourth day in a row to advance past Saturday's quarterfinals. Williams, the fourth seed, knocked out defending champion Bradley Klahn of Stanford 6-4, 6-4, and Sandgren beat Mississippi's top player Marcel Thieman 6-3, 6-4.

Now, the two Vols face an opponent where a scouting report is hardly necessary: each other.

Williams and Sandgren have been teammates at Tennessee for two seasons and friends for much longer than that. Williams is a Knoxville native and Sandgren grew up in Gallatin, so the two of them have played tennis together for years at every level of statewide or national competition.

Last summer, they toured the country playing tournaments as part of the USTA Summer Collegiate Team. They played at positions two and three in the Vols' singles lineup this spring and shared a court as doubles partners, racking up a 20-4 record together.

On Sunday, they will play on the same court again, albeit on opposite sides.

"We hit before every one of our dual matches," Sandgren said. "We practice a lot together and play a lot of points. We both know each other's game, pretty much inside and out."

Williams and Sandgren have been roommates for the last year at Tennessee and have spent the last two weeks in the same hotel room in Palo Alto during the Vols' stay at the NCAA Championships. Both jokingly said they intended on pranking each other to gain a competitive advantage, but they will mean business when they step out on the court with a trip to the finals on the line.

Every normal routine will be observed, including warming up together an hour before the match.

"This happens in tournaments -- you have to play your best friends," Williams said. "Growing up, you get used to it. You know you're not going to be nice to each other on the court. Off the court, you can joke around and be friends afterwards."

Williams earned his trip to the semifinals on the strength of his service game. He broke ninth-ranked Klahn early in both sets and just held serve the rest of the way, hitting numerous aces and keeping the defending champion off balance. Williams faced only one break point the entire match.

"I was serving out of my mind," Williams said. "My serving ability kept me in games and dug me out of holes. The serve helped me so much today. I've really been working on it, and it's obviously paying off."

With the victory, Williams tied his freshman win total of 41.

Sandgren, ranked 45th nationally, had never played a national collegiate tournament until this week, and he has made the most of his first opportunity, rattling off four wins against top-50 opponents.

He had a little difficulty closing out his quarterfinal match against 36th-ranked Thiemann. While serving for the match at 5-4, he fell behind 0-40 but reeled off five consecutive points to seal the 6-3, 6-4 victory.

The winner of Sunday's all-Vol semifinal meeting will become the third Tennessee player to reach the NCAA singles final. Associate head coach Chris Woodruff won the tournament in 1993. The only other Vol to earn finalist honors was John-Patrick Smith, who advanced to the finals as a freshman in 2008 and ended his career Friday after bowing out to top-seeded Steve Johnson of Southern California in three sets.

"It's going to be fun," Sandgren said. "I'm just excited that a Vol will be in the final. Win or lose, it's really exciting for me. Hopefully, one of us can come away with the championship."