McDonald has been hit by balls before, and has been struck in the chest a few times, but never his face.
"I can't imagine what it would feel like," he said.
Chapman was struck in the face by a line drive from the Royals' Salvador Perez, and is expected to be sidelined at least six weeks.
"For me, it's something you think about occasionally, and then you see something unfortunate like that," Jake Arrieta said. "I felt not only bad for him but his family and teammates. It's not something you ever want to see. I hope he recovers quickly and can get back with his team.
"We realize we're 60 feet from that hitter, who can generate a lot of power," Arrieta said. "Reacting to something like that is extremely hard to do. It's a scary situation and something we have to deal with and prepare for as best we can."
Arrieta remembers being hit in the face when he was in high school, taking a fastball off the orbital bone on the left side of his face, but he was batting.
The proposed protective helmets wouldn't have helped Chapman.
"It hit him in a really bad spot," Arrieta said. "Unless we go out there wearing a cage, those kind of things will happen. We're all aware of the issue, but there's only so much you can do without putting a cage on a guy's head. We just have to do everything we can to be in a position to defend ourselves."
Cubs manager Rick Renteria missed a year after he was struck in the face.
"For me, it was a little different," Renteria said. "He was on the hill, I was on second base and got hit with a line drive. What kept me out again was they had to re-break my jaw and do another surgery to correct the way it settled. I think once you get back on the field and you start getting back in the rhythm, you just go out there and don't even think about it anymore."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.