Don't expect anything more than the heat from Mariners' David Aardsma

PEORIA, Ariz. — Best to get a look at those sliders David Aardsma plans to throw down here while you still can.

As he does every spring, the Mariners closer will spend these preseason workouts honing the secondary pitches used on rare occasions when he feels his trademark fastball won't do the trick. But the guy who led the majors with 87 percent fastballs thrown last year isn't ditching his bread-and-butter heater, even with skeptics claiming too much reliance on it could be dangerous.

And that's because Aardsma says a fastball pitcher is exactly what he is and trying to be something else for variety's sake would be even riskier.

"When your goal is to throw 12 pitches, if they're not hitting it, they're not hitting it," said Aardsma, who enjoyed a breakout, 38-save season last year while averaging 10.09 strikeouts per nine innings. "Until the hitters show you something, then you don't change on them."

Aardsma said there's a big difference between a starting pitcher facing the same hitters three times in a game and needing to switch things up and a closer only seeing them once. In the case of that closer, he added, it makes sense to go after hitters with their best pitch until it doesn't work.

And the 95 mph fastball deployed by Aardsma did indeed work for most of last season. Aardsma took over the closer role in May and held opponents to a .196 batting average while posting an earned-run average of just 2.52.

He had searched for a mound identity in parts of four previous seasons with various teams. But it wasn't until he arrived in Seattle last year that everything clicked.

Under the tutelage of bullpen coach John Wetteland, one of the most successful closers of the 1990s, Aardsma found the identity he'd sought. Wetteland encouraged Aardsma to understand that he's a fastball guy and to throw each pitch with the conviction that his best stuff is good enough to get hitters out.

"John was telling us this just yesterday, that pitching isn't necessarily throwing a different pitch just because you have to," Aardsma said. "It's beating people. It's winning. If you're beating someone, you're pitching. Because you're smart enough to not change."

The other key was Wetteland, pitching coach Rick Adair and manager Don Wakamatsu convincing Aardsma he didn't have to blow hitters away by overthrowing. They told him his fastball could still get hitters out if he took a little off it in order to hit his targets more consistently.

"If your strength is a fastball, then your strength is a fastball," Wetteland said. "Just work on where you can control it to all spots of the zone. Get the control down to the point where you can do what you do best."

Aardsma worked on just that and his walk-rate fell from 6.47 per nine innings the prior year to a career-best 4.29.

"The key to me was, if I was already beating them with my fastball, don't try to throw it any harder," Aardsma said. "Whenever I get in trouble, it isn't because I'm throwing fastballs, it's because I'm getting behind in the count with them."

Aardsma knows the entire universe is aware he's going to throw a fastball most of the time, but points out everyone knows Mariano Rivera is likely to throw a cutter and still can't do anything about it.

"I know I don't have a track record beyond the one year," Aardsma said. "And let's face it, until I do, there are always going to be questions about me."

One of those surrounds Aardsma's lower-than-average home-run rate on fly balls — which pitchers throwing high fastballs tend to give up — last season. Since current studies suggest pitchers have little control over whether or not fly balls leave the park, there's a theory that Aardsma got "lucky" he didn't yield more game-blowing homers.

But until Aardsma stops being successful, he's going to keep doing what's worked.

"If I see that they're cheating just a tiny little bit on my fastball, then I'm going to throw them the split, throw them a slider," he said. "I may only throw those 5 percent of the time, but if the hitters have that 5 percent in the back of their mind, then it makes it easier to do what I have to do."

And do it he will. With as many fastballs as it takes.

Geoff Baker: 206-464-8286 or gbaker@seattletimes.com.