PORT ST. LUCIE, Fla. -- The blazing fastball of relief pitcher Matt Lindstrom, which has been clocked as high as 102 mph, isn't quite as effective or intimidating if the right-hander isn't able to find consistency with some of his secondary pitches.

That's why Astros pitching coach Brad Arnsberg pulled Lindstrom aside following his first outing of the spring March 5 against the Tigers in Lakeland -- a 37-pitch pitch exercise to get two outs -- and suggested he try a new grip on his slider, one in which he's holding his fingers closer together on the seams.

In five spring outings since, he's pitched six scoreless innings and has allowed one hit and no walks while striking out five. Lindstrom, whom the Astros acquired in a Dec. 9 trade from the Marlins, has made a strong case to be the team's closer when the season begins April 5.

"I'm getting guys check-swinging on the slider, and I feel like I can throw it for strikes more," said Lindstrom after throwing a scoreless inning in Wednesday's 5-2 loss to the Mets. "That's the key, for sure. Obviously everything comes off the fastball and locating it, but I think my secondary pitches are still coming.

"I've seen some pretty good results so far this spring, being able to throw them for a strike and also throwing them down and in to lefties," he said. "It's still coming along, and I'm glad we have another week and a half to work on it."

Lindstrom, 30, was one of the Astros' biggest offseason acquisitions, a power arm to add to the back end of the bullpen following the departure of closer Jose Valverde and setup man LaTroy Hawkins in free agency. He and Brandon Lyon, who signed a three-year, $15 million deal with Houston, entered the spring competing for the closer's job, but Lyon has appeared in only two games after having a cyst drained in his right shoulder.

In 191 career games -- all with the Marlins -- Lindstrom went 8-8 with a 3.88 ERA and 20 saves in 171 2/3 innings, striking out 144 batters and walking 71. The scouting report on Lindstrom glows about his overpowering stuff and his tendency to challenge hitters, but it raises concern about inconsistency with his command. You don't have to remind the right-hander.

"We're just looking for more consistency," he said. "The grip I'm using right now is allowing me to throw [the slider] like a fastball, and it's coming out of the same arm slot. Obviously, everyone knows pitching is upsetting hitters' timing and stuff like that. It's been big for me so far, and I just have to keep getting more [consistent]."

Lindstrom is as interesting off the field as he is on the mound. A native of Idaho, he was a three-sport star in high school and as a teenager went on a two-year Mormon mission to Sweden, where his grandfather was born. He can speak Swedish.

Drafted by the New York Mets in 2002 and traded to the Marlins following the 2006 season, he began last year as Florida's closer and saved 15 of 17 games with a 5.89 ERA. He went on the disabled list in June with a right elbow sprain and missed 31 games, but when he returned Leo Nunez had taken over as closer.

"It was tough," he said. "Everyone knows that baseball is a really big mental game, and you have to keep yourself on an even keel, and I felt a lot of times last year I was trying to overwork myself because I was trying to play catch-up and stay strong and thinking I was going to lose my strength.

"It was up and down, but I feel a lot better about the way things are going now and just kind of getting that fresh start with a new organization," Lindstrom said. "I think we can win a lot of ballgames if everything comes together. Obviously, the key is staying healthy."

And so is getting an opportunity. Lindstrom appeared in only two Spring Training games last year for the Marlins, but he has been given a chance to iron things out in game situations.

"This year, I actually got a chance to work on things, get my feet wet and get some appearances and prepare myself to go out there and do the same thing during the course of a Major League season," he said. "That's going to pay big dividends, especially having a pitching coach that has shown me a few things and helped me get my secondary stuff over."

Astros manager Brad Mills said he would feel confident having Lindstrom as his closer on Opening Day, and a decision could be made within the next week. Lindstrom just wants to contribute in the back end of the bullpen.

"As far as anything goes after that, it's up to Brad [Mills] and what he wants to do," Lindstrom said. "I consider myself having the ability to shut down games at the end, but that's up to the manager. We'll just go from here."