Brennaman made a bet with bench coach Chris Speier that if the Reds ever hit a 10-game win streak, he would go bald. The Reds accomplished the feat July 29, in Colorado, and Brennaman stood by his word.
The excitement began to brew, and the 48-year broadcaster decided to make a fundraiser out of the event. If the Cincinnati community could raise $20,000, Brennaman would shave his head on the field after the game.
The city responded, raising more than double the asked amount from online donations, stadium drop boxes and local company contributions.
"I never dreamed it would ever get this big, I truly did not," Brennaman said. "I'm thrilled to death that it's raised a lot of money for the Community Fund. If it's got to go, then thank God somebody is going to benefit from it."
The exact date of the bet has still yet to be pinpointed, but Brennaman said the deal came about a couple months ago when the Reds were traveling home after a series sweep.
Brennaman and Speier struck up a conversation about the club's recent success, and Speier made the comment that he felt the Reds had the potential to win 10 in a row.
Brennaman disagreed, and the rest is history. Ten wins for the Reds resulted in a loss for Brennaman.
"I think anybody who knows me knows there have been times when I've opened my mouth and inserted my foot, and this was another one of those occasions," Brennaman said. "I can tell you without fear of argument that there is no man on earth who has had a more passionate love affair with his hair than I have."
Brennaman said he had initially forgotten about the deal, but was quickly reminded when he entered the clubhouse following the Reds' ninth straight win.
The Reds earned their 10th consecutive win of the season the following night, giving the club even more reason to celebrate.
"The guys were pumped because we knew he just said that off-handedly on the bus," said Reds pitcher Bronson Arroyo. "It was kind of a joke at the time, and then it started to get a little more serious. You never get to achieve some of those goals when people throw out those outlandish things. This one's coming true, so it's cool."
Brennaman never backed down on his word but made just one stipulation -- an actual barber had to do the cutting.
Several Reds vied for the shaving duties, but Brennaman called upon his barber of 23 years, Jeff Duckwall, to do the honors.
"I wasn't going to let anybody else do it," Brennaman said. "I talked to a lot of people and they said it's not as easy as it seems shaving someone's head, and you need a professional to do it. So the guy who's been cutting my hair for 23 years is going to strike all the blows and then will not have to worry about cutting my hair for probably three or four months."
With the barber's chair set up right on home plate, a still-packed house at Great American Ball Park watched Brennaman's white locks drop to the field.
"I'm trying to figure out what he's going to do with that hair after," said Reds manager Dusty Baker. "Are they going to make a grey man's weave? We'll see."
Afterward, wearing a T-shirt that read "I'm Still Me," Brennaman welcomed three young cancer patients from Cincinnati Children's Hospital Medical Center onto the field with him.
"My friend John was at the Children's Hospital the other day and a young lady said to him, a patient, 'On Friday night, Marty Brennaman will look like us,'" Brennaman said before kissing the children's heads. "And I can't begin to tell you how much that touched my heart and how thrilled I am to be a part of your world."
The new do tops off an exciting week of birthday events for Brennaman, who turned 70 last Saturday. The crowd sang "Happy Birthday" to him before his hair was cut.
After a Neil Diamond concert last week, a successful fundraiser Friday night and a postgame fireworks show -- which he promoted with a fireworks-themed headdress to signify the end of the festivities -- Brennaman was left with just one thought.
"It doesn't get any better than this," he said.