More than seven years later, the Miami Marlins are giving him a second chance.
The Marlins said Thursday that they have signed Greenberg to a one-day contract, effective Oct. 2, and will play him that day against the New York Mets. Greenberg made his big-league debut for the Chicago Cubs on July 9, 2005 against the Marlins, getting one plate appearance but no official at-bat.
"I'm extremely proud to extend this opportunity to Adam," Marlins owner Jeffrey Loria said in a statement. "He has earned this chance as his love and passion for the game never diminished, despite his career tragically being cut short."
The Marlins announced their intention to sign Greenberg and play him Tuesday on NBC's "Today" show.
"I can't address and express how much it means to me," Greenberg said after Marlins president David Samson told him he would be playing on Tuesday.
Greenberg, a left-handed batter, went to the plate as a pinch-hitter to face the Marlins' Valerio De Los Santos with one out in the ninth inning of the Cubs-Marlins game. De Los Santos' first pitch sailed up and in, striking Greenberg in the back of the helmet, the force being such that the helmet flew off and the ball ricocheted up the third-base line.
Greenberg tumbled to the dirt, both hands holding the back of his head. He has often described that moment as feeling like "my head exploded." He awoke the next morning with symptoms of a concussion — unable to focus and feeling nauseous when seeing bright light.
After struggles in the minors the next season, the Cubs released him in June 2006. Greenberg had chances with other minor-league teams, but never made the majors again.
"I look forward to seeing Adam step up to the plate and realizing his comeback dream," Loria said.
Greenberg is one of only two players in baseball history to be hit by a pitch in his first-and-only major-league appearance and never take the field, the other being Fred van Dusen, who endured that fate with Philadelphia in 1955.
He and Marlins outfielder Justin Ruggiano once were teammates with the Double-A Jacksonville Suns, playing together there in 2006.
"Woke up (this) morning to find out Adam Greenberg and I will be teammates again this year! Dude can play," Ruggiano wrote on Twitter early Thursday. "Looking forward to Oct. 2."
Greenberg faced De Los Santos again in 2011, hitting a single off him as a member of the Bridgeport Bluefish in the independent Atlantic League. He also recently played for Israel in the qualifying rounds of the World Baseball Classic in Jupiter, Fla., walking in his only plate appearance there.
Greenberg was the subject of a campaign called "One At Bat," which lobbied teams to give him a second chance. As of Thursday morning, nearly 25,000 people had signed the online petition urging any major league club to give Greenberg an opportunity — since his first appearance in the majors did not count as an official at-bat, just merely a plate appearance.
"You better be ready," Samson told Greenberg.
Greenberg's reply: "I'll be ready for it."
The Marlins say Greenberg will donate his one-day salary — a pro-rated share of the minimum contract, about $3,000 — to the team's foundation, which will in turn donate to the Sports Legacy Institute, a group that furthers the study, treatment and prevention of the effects of brain trauma in athletes and others.