Jay Bruce followed with his first hit of the game, a ground ball single through to left field to bring Dioner Navarro to the plate.
Navarro worked Axford to a full count, blasting two long flies foul down the right-field line before ripping a 3-2 curveball into the gap in right-center field. The triple scored Bruce from first, gave the Reds a 2-1 win and made Navarro the hero for the second time in three days.
"It's a great feeling, man," said Navarro, who was 2-for-3 with two RBIs in Wednesday's 4-2 win. "It was a tough at-bat. I just wanted to put the ball in play and make something happen. I knew Jay was going to be running, and I tried to make something happen. Fortunately enough, the ball found the gap."
The Reds' 11th walk-off win puts them at 94-62 on the season and just behind the Nationals (95-61) for the best record in the National League. Washington defeated Philadelphia on Thursday night.
After finishing in the top 10 in the NL in runs scored in every month this year, the Reds have posted just 72 runs so far in September -- the second fewest, ahead of the Dodgers.
With just six games remaining, is it time to push the panic button?
"Not at all," said bench coach and acting manager Chris Speier. "I think if we would be in St. Louis right now wondering if this was it, then you might be a little bit concerned. Don't get me wrong, good pitching is going to get good hitting out ... so I don't think there's any concern."
Frazier's home run snapped a 16-inning scoreless streak after the Reds were shut out in the final eight innings of Wednesday's contest and the first eight frames Thursday.
"I've felt comfortable in every at-bat I've had this past week. I just couldn't really put anything together," said Frazier. "You don't want it to happen late in the year, but at the same time, we still got six games to get things going. Luckily for our pitching staff, they've been doing it all year. We'll be fine."
The pitching staff did its part Thursday, in particular Mat Latos, who held the Brewers to one run -- a solo homer from Carlos Gomez in the third -- on three hits through seven innings of work.
Despite finishing without a decision, Latos posted another quality start and continued his recent hot streak. Dating back to his final outing in August, the 24-year-old righty has gone six straight starts without a loss, giving up a total of 11 runs in that span.
Latos is 13-4 with a 3.52 ERA this season, posting the fewest losses of any Reds starter. The second closest is Johnny Cueto, with nine.
Thursday marked Latos' 32nd start of the season, and he eclipsed the 200-inning mark for the first time in his career.
"I've been healthy all year, thank God. Everything is right," Latos said. "I'm just happy for everything that's been going on this year. I'm happy with my performance the whole year. I'm happy we're winning ballgames."
Latos has one more start, which is slated for Tuesday at St. Louis before the Reds enter the playoffs.
The win gave the Reds 50 regular-season wins at home -- their most since the 1993 club won 49 games -- and delivered a crushing blow to the Brewers, who trail St. Louis by four games with six to play for the second NL Wild Card.
"This was a game we could not afford to lose," Brewers manager Ron Roenicke said.
Only 23,411 were in attendance to watch the regular-season home finale, but the crowd gave the Reds a total of 2,347,251 on the year, marking the second-highest in Great American Ball Park history, trailing 2003.
"It's good for the fans," Frazier said of the exciting ending. "They stayed around again. It goes to show you their faithfulness and how much faith they do have in us and we have in each other."