"I just turned around and put him on the bottom," Diaz said on the CBS News Early Show. "As soon as I was attacked, both teams, all the players, were out there to protect me."
Known as Comiskey Park when Kansas City coach Tom Gamboa was attacked last September, also at first base, the facility is now called U.S. Cellular Field after a $68 million naming rights deal was reached before the season.
As the host for this July's All-Star game, the stadium has already undergone a major sprucing up. Now it has a black eye, its safety record questioned by yet another ugly incident at a Royals-White Sox game.
"I don't believe that really reflects who we are as Chicago people," said White Sox manager Jerry Manuel. "Something has to be done to really put a stop [before] it becomes somewhat unsafe."
"As a major league baseball player, you shouldn't have to worry about your health on the baseball field from the fans," Kansas City first baseman Mike Sweeney said. "When they come on the field to do harm, that's when it gets scary."
Chicago Police spokeswoman Officer Alice Casanova said the man, whom she did not identify, was taken to St. Anthony's Hospital in Chicago for treatment of minor injuries, but the hospital would not confirm that.
Police will determine if he will be charged with a misdemeanor or felony based upon Diaz's injuries, Casanova said.
"I was in the Marine Corps Reserves, so I guess the training that they gave me for hand-to-hand combat kind of helped out a little bit there," Diaz told Early Show co-anchor Harry Smith.
Several Royals players could be seen kicking and stomping the fan while he was pinned down. When the attacker was put into a police car, his head was wrapped with a white bandage, soaked with blood near the right temple.
Royals right fielder Brandon Berger, who caught the ball for the final out of the inning, was one of the first to reach Diaz.
"You catch the ball, you look down and a guy's getting tackled and it's like, 'What's going on?'" Berger said.
Eerily, it was the first appearance by the Royals in Chicago since Gamboa, then Kansas City's first base coach, was attacked last Sept. 19
"We spoke about it in the locker room, this is where Tom Gamboa got attacked. We thought nothing was going to happen, but it was a full moon out there," Diaz said.
Now the Royals' bullpen coach, Gamboa said he thought security was tighter for his team's return. He felt safe — at least before the game.
"I think people just have too much to drink," he added.
Earlier, Tuesday night's game was delayed three times when fans ran onto the field before being tackled by security guards. All three were charged with trespassing, the White Sox said.
"I don't know how many people jumped on the field," said Royals catcher Brent Mayne. "They've got to get security along the lines or something because that was just kind of disgraceful."
"I don't know how it is when other teams are in town, but it seems like every time we are here, something crazy happens," Sweeney said. "Maybe they should bring more police in or put up some high fences so fans don't get on the field."
The White Sox said it was the actions of a few who don't represent their true fans.
"It happened last year. I guess someone wanted to do a copycat," said White Sox designated hitter Frank Thomas. "We just hopes this will cease because it's bad for baseball, it's bad for family members who are here."
The 55-year-old Gamboa still has a minor hearing loss in his right ear from last year's attack.
After Tuesday's incident, the Royals scored four runs in the top of the ninth for an 8-5 win — their 11th victory in 12 games, one overshadowed by the attack.