Team medical director Dr. Timothy Kremchek said Chapman could begin throwing off a mound in six to eight weeks, a timetable that could get him back in games in late May. The left-hander with a fastball that has reached 105 mph could start exercising and throwing on flat ground in a couple of weeks, Kremchek said.
The doctor called Chapman "a very lucky guy."
The surgery was performed by cranial facial plastic surgeon Dr. Ed Joganic.
Kremchek said earlier that a metal plate would be inserted in the bone above Chapman's left eyebrows and would remain there permanently. Chapman has a very mild concussion but no other brain injury and no injury to his eye, Kremchek said.
"He's feeling better and he has some pain management. We're optimistic that he is going to be on the mend," Reds manager Bryan Price said after meeting with players Thursday morning at the team's spring training facility. "Obviously, we'll stay in touch. We will make sure we follow the process as we continue to get familiar with the injury itself. We will let him know how much support he has and that we care about him. Hopefully, we will see him here very soon.
Cincinnati catcher Brayan Pena, a fellow Cuban and Chapman's close friend, was one of several Reds players who visited the injured pitcher Wednesday night and spoke to him on the phone Thursday morning.
"He was talking to me and we joked a lot," Pena said. "He just wanted to make sure for me to tell everybody that he appreciate so much the fans' prayers, especially our teammates, our coaching staff, everybody around, how much support and how much love he received and got from all of us."
Pena said Chapman was very happy when they spoke Thursday, "talking and joking. He was talking a lot about some Cuban jokes and that's good because that means his memory is still working pretty good."
The frightening incident, widely available on video via the Internet, occurred in the sixth inning of Wednesday night's game at Kansas City's spring training facility in Surprise, where the Royals' Salvador Perez lined Chapman's 99 mph fastball into the pitcher's face. Chapman was knocked backward to the ground, then rolled on his face, kicking in pain.
Pena rushed to the mound.
"Honestly, when I saw it I wanted to cry," Pena said. "That was my first feeling because it was very scary. It was very scary because I saw the line drive going straight for his face, and then I saw him bleeding and kicking and moving around the way he was."
Pena said Chapman "wasn't even talking. He was just like moaning and making sounds and then when I got there I panicked because I didn't know what else to do. Then the medical staff guys got there, and those guys were great."
Chapman was taken off the field on a stretcher as the crowd fell into an eerie silence and the game was called.
The pitcher was taken to a nearby hospital, then transferred to Banner Good Samaritan Medical Center in Phoenix. Kremchek said he expected Chapman to remain hospitalized for a couple of days and perhaps get released on Saturday.
The ball hit Chapman in one of the most protected areas of the skull, the doctor said.
"If you get hit in the side of the head, that could be disastrous," Kremchek said. "Where Aroldis got hit, you don't want to say he got hit in a good spot because he's undergoing surgery, but it could have been a lot worse, a lot more injuries, a lot more permanent. He's very lucky."
The 26-year-old Chapman has a blazing fastball that regularly hits 100 mph. The two-time All-Star defected from Cuba in 2009 and made the Reds in his first season of 2010. He had 38 saves each of the past two seasons, with 122 strikeouts in 71 2-3 innings in 2012 and 112 strikeouts in 63 2-3 innings in 2013.
Price, a former pitcher, said pitchers are in a dangerous situation, "regardless of how hard you throw."
"It's hard to defend yourself from 53, 54 feet," the manager said. "And everyone finishes their pitches differently. Everyone is not in a perfect fielding position and even if you are there is no guarantee that you can protect yourself when a ball's hit that hard."
Major League Baseball approved a protective cap for pitchers this winter following several terrifying scenes similar to this one in the last few years. The hats were available for testing during spring training on a voluntary basis but most pitchers have rejected them. Besides, the hats would offer no protection to the face, where Chapman was hit.
Chapman particularly wanted to thank the Royals organization for its support and offer assurance to Perez that it is just something that happens in baseball and was not his fault.
Pena said he also felt some responsibility.
"I kind of blame myself a little bit because I could have called slider or I should have called changeup," Pena said. "That's your thought process. Everything goes through your mind and you're looking for answers. ... You kind of put yourself in that guilt feeling."
But Chapman, Pena said, told him "'You know, it's not your fault. I should have thrown slower.' I'm the one feeling very bad about it and he's the one that's cheering me up. He's the one in the hospital."