SURPRISE, Ariz. -- In a 2-2 count against Nicky Lopez during live batting practice on Tuesday, Brad Keller dropped in a curveball.

The hook took Lopez by surprise.

“I swung and missed and went, ‘Oh, he has that,” Lopez said on Wednesday morning. “His stuff looks sharp. Just throws off the timing completely.”

Keller described his offseason as “getting out of my comfort zone,” and it led to him bringing a new and improved curveball into camp, where he’s vying for a rotation spot in his final year with the Royals before free agency. To do so, he needed to make some change.

Keller’s 5.24 ERA in the previous two seasons was the seventh highest among pitchers who threw 200-plus innings in that time. Innings are valuable, but so are results. The Royals view Keller as a bounce-back candidate in the rotation, even after they moved him to the bullpen last year.

“I didn’t have great success the last two years,” Keller said. “Something’s got to change. I needed to venture out of my comfort zone, figure out what’s going on, what’s going to allow me to get better. I couldn’t keep doing the same stuff. And I’m happy with what I landed on.”

That started with a conversation with representatives from Driveline Baseball, the renowned data-driven training center. They reached out to Keller shortly after the season ended and expressed their interest in training and helping him. Keller was interested, too.

When the Royals hired pitching coach Brian Sweeney, Keller brought up the program. Sweeney was supportive, and they talked about what pitches to work on over the offseason.

Keller has thrown a curveball before, but not in games. He made it a focus this offseason to give him speed differential between a mid-90s fastball, a 92-92 mph sinker and a 87 mph slider. He also sometimes throws a 90 mph changeup.

“As a group, we talked about what it would look like if he got something in the low 80s paired with his mid-90s fastball and everything in between,” Sweeney said. “So that was a focus of this offseason, find some sort of spin that would help with speed differential. He came in with some really impressive pitches.”

Sweeney gave Keller some ideas on pitch curveball grips, and Keller threw two bullpens at Driveline’s Arizona location. He went back to Florida with a ton of information.

“What [Driveline] taught me is what they’re talking about here [in camp],” Keller said. “It’s been good to have that similar way of thinking. I really liked it. I’ve never been really big on analytics, probably just because of knowledge. I just didn’t know much about it. Talking to all these guys here, they’re big into all the analytical stuff.

“Driveline taught me a lot of stuff, taught me feel, cues, grips. The whole motion capture to see some mechanical deficiencies. I got a ton out of it.”

To help the curveball, Keller added sweeping action to his slider to have two different movements on his two breaking pitches. His slider is still his best secondary pitch as a swing-and-miss option. The curveball is useful to throw hitters’ timing off -- in a live session last week, Vinnie Pasquantino grounded out to second, thrown off balance by the spin. Over time, Keller hopes the curveball can evolve to a swing-and-miss pitch.

“I can really see some guys hesitate before they swing,” Keller said. “That’s ultimately the main reason why we did it. And having another pitch I can go to is going to be big for me.”

Keller showed up to camp slimmer and stronger. Driveline also had suggestions for his delivery and moving down the mound faster was one. He’s felt the difference.

“I feel like it’s helped me out a lot this spring so far,” Keller said. “Not only with the pitches, but the command of everything has gotten a lot tighter. I feel like that’s how I used to pitch, just moving fast and pounding the zone. So, it’s been cool to get back to that and feel that again.”

With Zack Greinke, Brady Singer and Jordan Lyles seemingly locks for the rotation, the Royals have six or seven arms competing for those final two spots. Keller’s name comes up frequently when talking about the leading candidates of that group.

The curveball is a big reason why.

“Now he’s getting used to it because he’s got a different pitch and a different plan of attack,” Sweeney said. “What does it look like against the hitter? That’s why we’re here in Spring Training."