SAN FRANCISCO -- The bullpen door opens at Great American Ball Park. In almost a saunter, out walks closer Aroldis Chapman. After a brief pause, the jog to the mound begins and the anticipation for the final three outs builds.

Cue the music -- it's an intense guitar-laden opening from Rage Against the Machine's "Wake Up."

The Reds have had a parade of closers with various levels of effectiveness for the past several seasons. But this year, Chapman and his triple-digit velocity provided previously missing electricity in the ninth inning that had fans in the ballpark on the edge of their seat and viewers at home stopping what they were doing to pay attention.

As David Letterman often quips, possibly appropriate to Chapman's entrance music, "Wake up the kids and pour some black coffee down them. They won't want to miss this."

Reds vs. Giants

"When he's in and the fans are fired up, I think it's better when the fans get more crazier. It's weird to say that," Reds infielder Todd Frazier said. "I think he enjoys that more than a little bit quieter crowd. I think he feeds off of that."

Even on the road, opposition fans take notice when the left-handed Chapman reaches 100, 101 or 102 mph on the radar gun. Most are well aware that during the regular season, the "Cuban Missile" reached a record 105.1 mph at San Diego in September, 2010, during his debut season.

Chapman, 24, didn't come close to hitting 105 this season, but did something far more valuable for the Reds by being consistently dominant for long stretches. In 68 games, he posted a 1.51 ERA and 38 saves in 43 chances. In only 71 2/3 innings, he recorded 122 strikeouts for an average of 15.32 strikeouts-per-nine innings. And by taking a little off of the velocity, demonstrated more control, as he had only 23 walks.

The Reds had a 60-8 record in games where they used Chapman.

"It's huge, throwing 98 plus every time he's out there and healthy," Frazier said. "The only thing I worry about is when a lefty is up and I'm playing third, or when a righty is up and I'm playing first. That lined shot -- because they're going to be late on it."

What's all the more remarkable is that Chapman didn't move into the closer's role until May 20. And he missed nine games with left shoulder fatigue in September.

"He's growing into the role," manager Dusty Baker said after Chapman was shut down last month. "He's growing into the workload. We've monitored him about as close as you can monitor a guy. He's still learning the role and what the workload is off the field, so you don't wear yourself out training and you save enough for the game. But if you don't train some, then you can fatigue and lose strength if you don't train enough. He's still learning. The guy works hard."

How the Reds arrived at having Chapman work in the ninth inning was unintentional from onset of 2012, when he was expected to move from a bullpen setup role to the starting rotation.

Free agent Ryan Madson was signed to be the original closer, but became one of three relievers to be shut down with an injury during Spring Training. Madson missed the entire year after blowing out his elbow. Lefty Sean Marshall was promoted out of camp to closer, but was unable to shut down opponents as effectively as he later did in a setup role.

Enter the ultimate Plan C.

From June 26-Sept. 4, Chapman converted a Reds record 27 consecutive saves. For a stretch of 23 straight appearances, he did not allow a run. Nine different times this season, he struck out the side. For a Reds bullpen that led the Majors in ERA, there was no better anchor.

"I went to the bullpen and did the job they told me to," Chapman said in late August. "Then I became a closer and did my job as a closer. It started getting as it is now. I started liking it. Now I know if one day, I have to be a closer, I know I can do it. Right now, I'm really liking what I'm doing."

Chapman endured two rough stretched this season, and his failure was nearly as spectacular in scope as his successes have been. For a two-week span in June, Chapman went 0-4 with an 11.37 ERA and two blown saves over seven games. From there, he rebounded for his 27 straight saves.

On Sept. 10 vs. the Pirates, Chapman showed decreased velocity in the more human 93-95 mph range, as he walked three batters. He was removed in the middle of an inning for the first and only time this season, which led to his 10 days of rest.

Chapman has made four scoreless appearances since his return on Sept. 22, and will enter the postseason on a high note. In recording his 38th and final save at St. Louis on Tuesday, 13 of his 16 pitches reached 100 mph or higher. The radar gun showed 102 mph six times.

"Since the return to pitching, today has been the best day -- not just physically but on the mound. I felt really good on the mound tonight," Chapman said that night.

With that effectiveness and the ability of the Reds bullpen to shorten games, Cincinnati has another reason to feel confident in the postseason.

"It's fun watching him," Frazier noted. "A lot of fun."