After being treated for at least 10 minutes, Chapman was lifted onto a cart and taken to an ambulance as the crowd of more than 6,000 applauded him. Umpires then called off the game.
The Reds said Chapman was taken to Banner Del E. Webb Medical Center in Sun City, where tests indicated fractures above his left eye and nose. He was transferred to Banner Good Samaritan Medical Center, where he will undergo further testing. He will be kept overnight for observation.
"You just can't find it in your heart to go out there and play," Price said. "Baseball is a game to be played with a lot of joy in your heart and determination and focus. I don't think anybody was able to do that after that moment."
Umpires crew chief Chris Guccione said the players, staff and umpires were "too rattled" to continue and the managers stopped the game by mutual agreement.
"The fun goes out of it all," Royals manager Ned Yost said. "It's just not a productive atmosphere to continue game. We all play this game but nobody wants to see anybody get hurt ever, and when something like that happens, it's a feeling that affects both teams."
After Chapman fell to the ground, players and coaches gathered around the mound as he was treated. Perez knelt at the edge of the mound in the silenced stadium. Chapman's father, who was at the game, also came on the field.
The Royals were ahead, 5-3, when Perez batted with the bases loaded and two outs in the sixth. His line drive on an 0-2 pitch went off Chapman's head and bounced toward the Royals' dugout on the third-base side. Chapman had come into the game at the beginning of the inning and had issued four walks with a double play intervening.
The game went into the books as a 6-3 Royals win. On the final play, Perez was credited with a single and Danny Valencia scored from third base.
Before the incident, leadoff batter Billy Hamilton got Royals starter Jeremy Guthrie's outing off to a rough beginning, slamming an 0-2 pitch into the right-field bullpen for his first homer. Skip Schumaker followed with a double to deep center field and took third on Todd Frazier's looping single.
When Jay Bruce struck out and catcher Perez's throw caught Frazier in a rundown between second base and first, the Royals became so preoccupied with tagging him out that they neglected the runner at third. So Schumaker just sprinted home. The Royals got their double play but the Reds got a second run.
The Royals jumped ahead, 3-2, in the second inning against Alfredo Simon, although two runs were unearned. Perez walked and scored on Mike Moustakas' double to right-center field -- his 16th RBI in 16 games. Shortstop Zack Cozart couldn't handle Lorenzo Cain's hopper. After Cain swiped second, Norichika Aoki pulled a two-run single into right field.
Eric Hosmer's two-run double down the left-field line put the Royals up, 5-2, in the fourth.
Guthrie was pulled after 86 pitches with one out in the sixth inning. He gave up three runs on five hits and three walks. Simon also made 86 pitches in his five innings, touched for five runs on eight hits and three walks.
Up next:The Royals' Bruce Chen and the Angels' Jered Weaver, who dueled for six scoreless innings in the 2012 season opener at Anaheim, are matched again in Thursday's 3:05 p.m. CT game at Surprise Stadium. (After Chen left that game, the Angels broke loose for a 5-0 victory.) Greg Holland and Wade Davis, who pitched in a Minor League game on Wednesday afternoon, will return to test their arms on back-to-back days. Kelvin Herrera is also scheduled to pitch in relief for Kansas City. The Angels also have scheduled Joe Smith and Kevin Jepsen to pitch.