CINCINNATI — Aroldis Chapman was too fast to hit.

Soon, the Cincinnati Reds could be too far ahead to catch.

The Cuban defector made an eye-opening big league debut, topping out at 102 mph during his perfect inning, and the Reds added to their rapidly growing lead in the NL Central by beating the Milwaukee Brewers 8-4 on Tuesday night.

Cincinnati wrapped up the best August by any team and moved a season-high seven games ahead of St. Louis, which lost to Houston 3-0. The Reds haven’t led by so many games since 1995, the last time they reached the playoffs.

Now, they have a radar-busting reliever to help them get there again.

“Aw, that was a wonderful debut,” manager Dusty Baker said. “People expected it, and they got what they heard about and read about.”

It was almost too fast to follow.

Chapman joined the Reds’ bullpen and matched the hype his first time out, throwing four pitches clocked at 100 mph or better. The Reds called up the hard-throwing lefty, hoping he can add some sizzle to their September — and beyond.

“It’s a big thing for me,” the 22-year-old Chapman said, speaking through a translator. “Being able to come up and pitch not only here, but to pitch for the Reds in the playoffs would be something great for me, to keep going with the team and someday get an opportunity to win it all.”

The Reds pulled away from the defending-champion Cardinals by going 19-8 in August, the best mark in the majors. Now, they have a pitcher who might be the next big thing.

From the start, the Reds had their attention on September.

They called up Chapman from the minors before the game, making him eligible for postseason play. Chapman’s fastball has been clocked as high as 105 mph in the minors, making him something of an urban legend before he even reached a major league mound.

Fans around the Reds’ bullpen in center were calling for him as the home team pulled ahead, wanting to see him toy with the big league radar guns.

“There were a lot of people down there,” closer Francisco Cordero said. “Even before he started throwing, they were calling ’Chapman, Chapman!’ It was amazing. It was a great night.”

Fans started snapping pictures when he took off his jacket and started warming up after the seventh-inning stretch. They cheered when Chapman — wearing No. 54 — was shown on the videoboard.

Chapman got a standing ovation from the crowd of only 19,218 when he jogged out of the bullpen to pitch the top of the eighth with the Reds leading 8-3. Fans let out a collective “ooh” after each high-velocity warmup throw.

Any nerves?

“Of course I was nervous,” Chapman said.

Didn’t show it. His first pitch to Jonathan Lucroy registered 98 mph, and the third one hit 102 mph, drawing a loud cheer.

Chapman made quick work of the three batters he faced — a strikeout by Lucroy on an 86 mph slider and two weak ground balls by Craig Counsell and pinch-hitter Carlos Gomez. Half of his eight pitches reached triple digits, topping out at 102.

He walked off the field to another standing ovation.

“I was just trying to hit the ball hard,” Lucroy said. “He is very deceptive. He kind of hides the ball. It’s tough.”

No one doubted those big numbers on the scoreboard.

“Sometimes the radar guns get pumped up,” Baker said. “That was a bona fide 100-102.”

Joey Votto drove in three runs with a pair of doubles off Yovani Gallardo (11-7), hearing “MVP!” chants each time he reached. Sam LeCure (2-4) pitched two innings in relief of Aaron Harang, who struggled in his return from back spasms.

Votto put the Reds ahead to stay with his first-inning double, which extended his hitting streak to 10 games. The first baseman has led the NL’s top offense in August, pushing his overall RBI total to 97. Scott Rolen broke the game open with a bases-loaded double in the sixth.

The Reds are trying to find out if Harang can help them down the stretch as a starter. He returned from a nearly two-month stay on the disabled list because of back spasms, and had a tough time. The right-hander left in the fifth after failing to retire a batter.

Harang took Counsell’s liner off his left foot in the fourth inning but stayed in the game.

Gallardo has struggled in his last three starts, giving up 20 runs in 15 innings. He allowed eight in five-plus innings on Tuesday.

NOTES: The Reds put OF Laynce Nix on the 15-day DL with a sprained left ankle, hurt on Aug. 23. They also optioned RHP Edinson Volquez to Class-A Dayton to make two starts, hoping he’ll fix problems with his delivery. … 2B Brandon Phillips was out of the lineup for the fifth straight game with a bruised right hand, which was hit by a pitch. … RF Jay Bruce was a late scratch with pain in his right side.