Later, after Gardner had left the field on a motorized cart and his teammates held their collective breath, he stood in front of his locker in the home Yankee Stadium clubhouse and considered himself extremely fortunate.
"I feel all right, just a little headache," Gardner said. "I should be good tomorrow. I guess it could have been a lot worse."
Gardner was examined behind the scenes and was cleared by the Yankees' medical staff, who seemed satisfied that the 25-year-old did not suffer a concussion. Gardner was scheduled to fly with the team to Florida immediately after New York's 3-0 loss to the Nationals.
"He knew where he was, and I saw him in the eighth inning," Yankees manager Joe Girardi said. "He said he was OK, he just had a headache."
The play occurred in the top of the eighth, as the Nationals' Austin Kearns hit a drive off left-hander Phil Coke that Gardner ran down in the gap, snaring the ball before ramming his back into the fence and crumpling to the warning track.
Gardner flipped the ball to left fielder Johnny Damon to hold the runner, Adam Dunn, at first base.
"I knew the ball was in my glove, I could feel it, so I just tried to flip it so they could pick it up instead of diving on top of me," Gardner said. "That's why I did what I did. I know I did something with it."
As Gardner lay on the warning track, the entire Yankees starting lineup ran out to the wall, save for Coke and catcher Jorge Posada. Gardner was attended to by head athletic trainer Gene Monahan and Girardi.
"I was kind of out of it when I was laying on the ground at first, but I have a pretty good memory of what happened," Gardner said.
The walls at the new Yankee Stadium are harder than at the old building, Damon said, and do not forgive when an athlete runs full speed into one. But Gardner did, left no choice in his pursuit but to make impact.
"Brett is capable of making those plays all the time," Damon said. "It's great to see when he's in the lineup because it seems like he can do something spectacular all the time."
The spot he hit was the Dunkin' Donuts sign to the left of the visiting bullpen gate, to the right of the 385-foot marker, an area that only features padding on approximately three feet of the 8-foot, 6-inch wall.
"I probably didn't realize I was that close to the wall," Gardner said. "I knew I was probably going to go into the wall, but I didn't know I was that close. Maybe my hip hit the wall first and my head slammed back into the glass. It was pretty hard."
At one point, Monahan appeared to use smelling salts on Gardner, who eventually sat up covered in dirt and some bloody scrapes, covering his face.
He sat up, wincing, and eventually walked slowly to the waiting vehicle as the remaining rain-delay crowd applauded. Gardner was replaced in center field by Melky Cabrera.
"It was a great play. It saved us a run, maybe two runs, and he sacrificed his body," Girardi said. "It's unfortunate that he had to be knocked out of the game, but that's the way Gardy plays. Gardy plays hard."
Gardner said that his teammates had expressed mostly concern about his well-being in clubhouse conversations, but said he would not shy away from watching it again should he come across it on television.
"I'll see a replay. Maybe I'll learn something from it," Gardner said. "Maybe I could have gone in a little differently and not have it hurt so bad."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.