Before Friday’s game, Mariners rookie shortstop Brad Miller was joking about how when he really gets hellbent on the basepaths, his limbs start flailing to an extent that an old coach once gave him the moniker “Crazy Legs.”

And then Miller went out in his new role as the Mariners’ leadoff man, and put those crazy legs into action.

He started the game off with a triple into the right-field corner, added another triple for good measure, and sparked Seattle to a 4-2 win over the Cincinnati Reds at Great American Ballpark.

“I like that style, hopefully stretching some singles into doubles and doubles into triples,’’ Miller said. “I’ve always been coached that way. And I like that, going all out until they stop you.”

Of course, it helps when the No. 2 hitter steps up and hits the ball out of the ballpark. That’s what fellow rookie Nick Franklin did in the first inning, on the first pitch he saw from Reds starter Mike Leake after Miller’s triple, to stake Mariners starter Aaron Harang to an immediate 2-0 lead.

“Brad set the tone right,’’ Franklin said. “I was just looking for a pitch to drive. Usually, I want to see a pitcher for the first time, but at that point in time, I said, you know what, I’m going to try to jump on anything that looks good.”

That explosive start energized the Mariners, said Michael Saunders, who would add his own contribution to Seattle’s third victory in four games on this trip.

“To give our pitcher a lead like that, it kind of brings the momentum into our dugout and we kind of just kept going,’’ Saunders said.

The Mariners extended the lead to 4-0 through their half of the fourth on a homer and sacrifice fly by Saunders, then hung on for dear life.

Ultimately, it was their bullpen that did the dirty work after the Reds crept back in it with runs in the fifth and sixth off Harang. Yoervis Medina, Charlie Furbush and Oliver Perez held the Reds hitless over the final three innings, striking out six, to make a winner of Harang in his return to Cincinnati. Perez struck out the side in the ninth for his second save.

“Great job by all those guys, and we had Tommy (Tom Wilhelmsen) waiting,’’ Wedge said. “If Oliver didn’t get that guy, Tommy was going to be in the game. With the left-handers and the way it lined up late, we felt good going to Oliver, and he was really good. Charlie bridging that gap was huge as well, and Medina did a nice job.”

But Wedge gave special mention to Miller, who not only became the first player with two triples in one game in the 10-year history of Great American Ballpark, but also the first Mariner to do so since Carlos Guillen on May 9, 2003 against the White Sox.