MESA, Ariz. -- The mystery has finally been solved. Rangers pitcher Dane Dunning -- who has been teasing a new pitch since January -- has finally decided to let everybody in on the secret. It’s a forkball.

When Dunning made his start against the Diamondbacks at Salt River Fields last week, Statcast registered the pitch as a splitter. The right-hander didn’t confirm or deny it at the time, but on Sunday when the Rangers faced the A’s at Hohokam Stadium, he finally confessed.

“I threw some good forkballs today, so that was fun,” Dunning said. “I had some good swings and misses on them. I think I threw four or five of them, all of them came in the third inning.”

In the Rangers’ 5-2 loss to the A’s, Dunning allowed four runs in three innings, but struck out five batters as he continued to work on the forkball later in his outing.

“Today was a big step for this spring,” he said. “I actually felt really good the whole time, and got unlucky in a couple situations. I felt like I filled up the zone well today and was able to locate with pretty much all my pitches. I was happy with how I pitched, but just not extremely happy with some of the results."

Dunning’s current arsenal includes a sinker (33.1% in 2023), slider (23.4%), cutter (20%), changeup (15.6%) and curveball (4.7%). He started playing catch with the forkball during the postseason last year and it spiraled from there as he looked for another effective pitch to play off his sinker-slider heavy mix.

“I went into the offseason and reevaluated myself and the changeup was an effective pitch, but it wasn't as effective as it should be,” Dunning explained. “For the most part I got whacked during the year. The forkball more or less came along and I went into the offseason like, ‘I'm gonna try throwing it and if it's good, it's good. If it's not, then I'll just wipe it clean and stick to my normal stuff.’ When I threw it, it had great shape, so I was like, ‘Alright, I'm gonna take it into spring.’”

Mets starter Kodai Senga’s best pitch is his “ghostfork,” but the forkball may be the rarest pitcher in MLB currently. The only other pitcher who threw a forkball last year was Rockies reliever Matt Carasiti, who is in their system but not currently on their 40-man roster.

In a perfect world where the forkball works exactly how he wants it, Dunning isn’t totally sure exactly how frequently he would like to use it in a typical start, but he did note he would like it to play similarly to his changeup.

“You’ve gotta keep the hitter guessing, right?” Dunning said. “I’ve gotta be a person that mixes. I’m still learning the pitch. I want to use it mainly to get back in counts and get hitters off balance with it and just show a different approach. But really, time will tell.”

Manager Bruce Bochy said, more than anything, he’s just happy to see Dunning do things to try to elevate his game, whether that’s a slight uptick in velocity or adding a new pitch or anything in between.

“He's got a lot of deception,” Bochy said. “He's not a guy where you look up there and he's [throwing] 95. But it plays like that because he hides the ball well and has the good slider, curveball and changeup. … He's trying to get better. He's experimenting with [the forkball]. We'll see how it goes, but I've seen some really good ones from him. It's a work in progress right now, but I just liked the fact that he's just trying to add to his repertoire.”

Robertson throws live BP

New Rangers reliever David Robertson threw live batting practice for the first time this spring on the backfields in Surprise. He faced big leaguer Josh Smith, Minor League catcher José Godoy, and an additional batter from Minor League camp.

Robertson faced nine batters, allowing one hit and striking out one. He threw 27 pitches, 17 for strikes. The right-hander said he typically ramps up slowly and he’s on track for where he would like to be at this point in camp.

Bochy has said that he would like to name a closer by Opening Day, and Robertson is no doubt in the mix, but he’ll let the competition play out over the next few weeks of camp.

“He got his work in,” Bochy said. “He used all his pitches. He said he just worked on throwing strikes, quality strikes and so it was a good day. It's good to see him out there as he gets things started.”