Police say a father and son ran onto the field at Comiskey Park and attacked Gamboa, who said after the game that he had no idea what provocation the men had.
The two, both shirtless and wearing blue jeans, ran dashed directly toward the Gamboa, 54, and knocked him to the ground with a series of blows.
"I was looking at the hitter in the box and it felt like a football team had hit me from behind," Gamboa said. "The next thing I knew I was on the ground trying to defend myself."
Asked if he heard either attacker say anything, Gamboa indicated one of the men was yelling at him, but he couldn't make out what he was saying.
"It just happened so fast I had no clue what he was saying," Gamboa said.
The entire Royals bench rushed to Gamboa's aid, pulling the two offenders off him.
"When I rolled over and saw there were two of them, I tried to kick one guy and the other guy smoked me on the side," Gamboa said. "Fortunately, my team got to me quickly."
Several players said they saw a closed pocket knife at the scene. Some said they saw it lying on the field. Others said it was in one of the attacker's hands as he charged Gamboa.
The assailants were handcuffed and hauled off by security to boos from the crowd.
"I was at the bottom of the pile," he said. "I saw I was bleeding and heard one of our players yell that one of them had a knife. I was stunned, checking to see if I'd been stabbed."
Fortunately, Gamboa, who spent the 1995-1999 seasons as an instructor and coach do the Chicago Cubs, suffered scratches on his forehead and was sore, but not seriously injured.
White Sox General Manager Kenny Williams visited Gamboa in the visitor's clubhouse after the game to check on his condition and apologize on behalf of the White Sox organization.
"It's disturbing, very disturbing," Williams said. "I am in shock and surprised like most of you. But we certainly feel it's pretty much an isolated incident."
While some initial reports indicated that the father and son had a verbal exchange with Gamboa during the game, the Royals denied any provocation.
Chicago first baseman Paul Konerko was one of the closest players on the field to the attack.
"By the time I saw them (the attackers) weren't saying anything," Konerko said. "They were on the ground and they were getting (beat up), and rightfully so."
"I don't think it's any indication of how Chicago fans are, but I didn't think two people like that existed on earth," said Royals first baseman Mike Sweeney. "It's just sad that two people have such low lives that they'd jump on the field and attack a first base coach for no apparent reason. To bring a knife with them on the field is just unbelievable. They should be held accountable for their crime. I think our team and Tom Gamboa should press charges to the fullest extent."
Royals closer Roberto Hernandez, who also pitched for the White Sox earlier in his career, said it's impossible to guarantee that incidents like this one won't happen again.
"Stuff like that is hard to control," he said. "Once fans start to get boisterous and have too many beers, all of a sudden it just happens. They walked off and suddenly attacked him. Those aren't true baseball fans, not even White Sox fans. They are just idiots. That's the dumbest thing I've ever seen."
Chicago police intend to charge the father with felony aggravated assault for striking Gamboa and a security guard, who is also an off-duty Chicago police officer.
One of the alleged attackers has been identified as William Ligue, 34. He is being held in jail on a charge of aggravated battery. His son was charged with the same offense, but as a juvenile.