RIO DE JANEIRO (AP) Never did Karch Kiraly expect the women's volleyball Group B winner to go unblemished.
He probably had little idea captain Christa Dietzen would be the one to deliver during the latest impressive U.S. victory, either.
Dietzen made the final kill of the third set and provided a big lift off the bench, helping the top-ranked Americans (5-0) put themselves in prime position in this Olympic tournament. They responded from a one-set deficit to beat China 22-25, 25-17, 25-19, 25-19 on Sunday, and now will face Japan in the Rio de Janeiro Games quarterfinals Tuesday at Maracanazinho arena. China must face two-time defending champion Brazil (5-0), which swept Russia in Sunday's late match and is yet to drop a set.
All along, Dietzen has accepted her role in Rio - limited or otherwise, like Sunday.
''I love whatever role I'm given, I think it's great to come off the bench, to be a starter,'' said the 29-year-old Dietzen, who has been working closely with team high-performance psychologist Michael Gervais during this trip. ''It's important for athletes to develop their ability to be their best from any position. When the team needs me, I'm ready to go in.''
Dietzen, nicknamed ''Mom'' by her teammates for all her care and used sparingly so far in Brazil, delivered. Her teammates couldn't have been more proud to see it.
''This team has just so much trust in her as our captain, and with the experience that she has she's a real stabilizing influence,'' Kiraly said.
They joke she's a ''caged lion,'' too.
''We call her mom, and she's more of a mom to me than anybody on the team,'' Kelsey Robinson said. ''She has been someone who has taken me under the wing since my first year. We'd go to lunch, she'd take me to dinner. ... I love the way she plays, I love the way she fights. For her to be such a great teammate in the role she's been asked to do and get her shot tonight, I'm so proud of her.''
China coach Jenny Lang Ping, who once coached the Americans, and Kiraly are both looking to become the first to win volleyball gold as a player and coach.
Kiraly certainly isn't getting ahead of himself. Sure, the U.S. took a nice step forward to the goal of reaching the top of the medal podium for the program's first gold ever.
The Americans, silver medalists the past two Olympics behind Brazil, dropped five sets in all.
''I'm more surprised that somebody went undefeated than they didn't,'' Kiraly said. ''We got pushed a lot, and that was all good for us.''
This marked the 11th meeting between the countries since the U.S. beat China for the 2014 world championship title. The Americans have won eight of 12 meetings since then. After a June 12 loss in China, the Americans bounced back with victories on June 26 in Hong Kong and July 8 in Bangkok.
On Sunday, Dietzen did the very thing veteran players do when called upon: She had herself ready for the moment when needed.
''It's very important for her to help their team when she's a substitute for the younger players, and the younger players are probably more calm to play,'' Ping said. ''She's a great blocker, too. Every time, she gives our attack lots of trouble.''
Earlier, Italy captain Antonella Del Core said a tearful Olympic goodbye.
She thanked everyone in the crowd over the public address system after her final match with the team and a straight-set win against Puerto Rico. Her Italian teammates threw her in the air again and again, and had written on their arms, ''Grazie Cap (hashtag)15'' with a heart.