MESA, Ariz. -- Sean Manaea's work-in-progress slider was in pristine condition Tuesday afternoon.
The A's lefty already had a good one, but he's often lacked the confidence to use it at his disposal. That wasn't the case in his Cactus League debut against the Rangers on Tuesday, which spanned two innings, as the A's went on to win, 5-3.
"It feels amazing right now," Manaea said. "I'm starting to get that confidence, even in warmups, throwing it for strikes, and it just feels really, really good right now."

Manaea walked two batters and allowed one hit, contributing to a rather high pitch count; limited to 50 pitches on the day, he needed 45 to get through two. But he struck out the side in the first, working around two baserunners, and got two ground-ball outs in the second to strand one.
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"He ended up getting the swings and misses that we wanted to see, used all his pitches," A's manager Bob Melvin said. "Starting out in a good direction for him."
The outing came one week after his originally scheduled start was postponed because of back tightness. Manaea had no issues with it Tuesday.
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"I know today was the first time out facing different hitters and I was a little amped up," he said. "Getting back out there, throwing two-seamers, they were turning into cutters because I was gripping the ball just a little too hard. That stuff happens, but I'm super excited to get back out there and keep progressing."
Manaea appeared comfortable throwing his breaking ball to both sides of the plate, a progression that's been ongoing. He utilized the pitch 17.37 percent of the time in 2017, as opposed to just 12.87 percent of the time in his first big league season. Batters missed on 89 of their swings against the pitch in '17 and hit just .174 against it.
Recently, Manaea has been playing around with grips and only recently moved his fingers ever so slightly in just the right place.
"Past couple years, I've just kinda been searching for it and nothing has really stuck or felt as good as it does right now," he said. "Just having that third pitch is so big."
It's not the only weapon Manaea wants to have in his pocket. Oakland's No. 2 starter is intent on being more aggressive in his third big league season. He had a 4.37 ERA in 29 starts last year.
"I feel like I'm a little too nice sometimes and that transitions onto the field, and I know if I want to be good then I have to be different on the mound," he said. "I kind of took that into today, and I didn't care who was in the batter's box, I was just attacking hitters. The mentality is so much better. It's crazy how just thinking differently can lead to good results."
Mateo debuts, Luzardo pitches in
Infield prospect Jorge Mateo took over at shortstop to begin the fifth inning for his A's debut, and struck out in each of his two at-bats.
"First time out, probably a little jumpy at the plate," Melvin said. "Hasn't seen a lot of live pitching, obviously, but it was just good to see him on the field. We told him he was going to be in the game, and he was on the field before they got off the field."

The speedy Mateo, ranked by MLB Pipeline as the organization's No. 4 prospect, was held out of game action early on because of a lingering left knee injury.
Yet another high-profile A's prospect, left-hander Jesus Luzardo, was awarded the ninth inning and pitched around a leadoff single, getting up to 96 mph. He's just 20 years old.
"You think it's a Spring Training game, but for him, you know his heart's pounding," Melvin said. "He's throwing 96 mph, has a better breaking ball than we thought, and he's got a plus changeup too. That's pretty impressive. We brought him over here to try to get him an inning. I didn't know that it was going to be the ninth, but that was impressive. It's nice to be able to reward a kid like that and get him in a game."