LAKELAND, Fla. -- Casey Fien has always been a strike-thrower. That was the calling card that earned him a trip or two across the street from Minor League camp last Spring Training. Now he's advancing as he delivers more strikes with a pattern that opponents don't want to hit.

Depending on how the Tigers' bullpen shakes out, that could earn him a jump to Detroit.

"All managers love strike-throwers," manager Jim Leyland said.

It was last Spring Training that Fien first caught Leyland's attention, enough to get him a couple of appearances as an extra pitcher against the Astros and Indians. He took that momentum and became a closer at Double-A Erie, striking out nearly a hitter per inning while allowing opponents a .228 batting average to earn an Eastern League All-Star nod.

It was a late-season stint at Triple-A Toledo that showed him the difference facing the veteran bats of the International League.

"When you're facing those type of hitters, they have an approach," Fien said. "They know what they can hit. They know their weaknesses and they know their strengths. So they're looking for that one pitch. If you throw it, no matter if it's good or bad, they're still going to hit it. And they can foul off the tough pitches and make you throw the next pitch.

"That's pretty much the whole thing that I learned at Triple-A. Those hitters are definitely hitters, and they know what they're doing. In Double-A, you have that with some of the guys, guys that can handle the bat, but some guys are just up there hacking."

After faring well at Toledo, Fien did much the same thing in the Arizona Fall League. His aggressiveness has stuck at every stage.

So far, it has continued in this camp. None of the veteran hitters of the Grapefruit League have hit him particularly hard this year. Since giving up a run on two hits to the Yankees on March 8, Fien has tossed four scoreless innings on two hits with a walk and four strikeouts. He has thrown nearly two-thirds of his pitches for strikes in the process.

Tuesday ended up being a quality test for him with back-to-back battles with Astros hitters, trying to avoid the pitch that would hurt him. He threw three straight sliders to Geoff Blum, trying to get him to chase in a long at-bat, before he eventually flied out to center.

"He had a better breaking ball than he's had," Leyland said, "and he threw more of them."

The mentality hasn't changed for him, but while doing a good job of reading hitters, he's also reinforcing the point of first-pitch strikes.

"I just stick to my game plan and attack," Fien said. "I'm going to get ahead first pitch and then I'm just going to try to make you chase my pitch, not make me throw what you want. I'm definitely going to come after you and try to get in your head, maybe back something up."

Nor do the Tigers want him to change much from the strategy that earned him a non-roster invite in the first place.

"He's a pitcher that's a ballplayer. He likes to play," Leyland said. "He's the [Will] Rhymes of a pitching staff -- good, but nothing fancy, not afraid."

Leyland has called Rhymes a "dirtball," his endearing term of the spring for a gritty ballplayer. He also has called Rhymes one of his bright spots of this camp. Fien was one of those bright spots last year who had no chance to make the club. Now he's making his case.

"You know what? My job is to make it as tough of a decision on them," Fien said. "If I'm up there, I know I can win games. And right now, everybody in the bullpen is throwing real well, so everyone's going to make it a tough decision. There's going to be some guys that have been throwing well that are going to get sent down, and I think they understand it. All we can do is make it tough on them, who they think is going to help out the club more."