Sometimes, left-hander Aroldis Chapman can’t help but peek.

A murmur will go through the crowd when one of his express-lane fastballs smacks the catcher’s mitt and the estimated speed is shown in triple digits on the ballpark scoreboard. The 22-year-old Cuban hears the commotion and can’t help but sneak a glance to see what big number has popped up.

“Once in a while, I take a look and, yeah, I get surprised and really happy to see what it is,” Chapman said.

From now on, scoreboard watching will take on a little different meaning every time he lets one fly.

Chapman made his big league debut with the NL Central-leading Cincinnati Reds Tuesday night and pitched a perfect inning. He threw eight pitches, half of them reaching at least 100 m.p.h. on the Great American Ball Park board. Two of them clocked in at 102.

Fans love the big numbers — the crowd roared every time one popped up during the 8-4 win over Milwaukee. But is there more to it than just the allure?

Sure is.

Just ask a hitter.

“The old adage is that speed kills, and it does,” Hall of Famer Joe Morgan said yesterday.

“Guys who throw hard are the most successful because there’s an intimidation factor in there, too. If a guy throws real hard and the ball gets there quick, there is a slight fear factor.”

A Louisville Slugger researcher pointed out yesterday that it takes little more than one-third of a second for a ball to travel the approximately 17 metres to the plate once it leaves Chapman’s hand at more than 100 miles per hour. That leaves a batter little time to make up his mind and start to swing.

Better not blink.

“The speed bothers you because you have to rush your swing,” Morgan said. “And the other (pitches) bother you because once you rush and something else happens, you’ve got to adjust to that.”