"It's not like I haven't been practicing it or anything," Romo said Sunday. "I don't need to throw it in a game for me to sit there and know that I've got it."
Romo's woeful spring numbers are almost certainly the result of his refusal to throw the pitch. After he allowed five runs without recording an out Saturday, Romo's Cactus League ERA ballooned to 33.00 with a WHIP (walks plus hits per inning pitched) of 4.67 in four outings.
But Romo isn't reaching into the well for his slider just yet. He's been throwing a strict fastball-changeup mix with the hopes of developing his changeup into a reliable third option.
Last season, Romo threw that changeup only 6.5 percent of the time, according to FanGraphs. But that number has risen in each of the past three years. If his work this spring pays off, he's hoping it'll rise again.
"It's coming along," Romo said. "I'm just working, you know what I'm saying? And I feel like I'm making progress, I feel like I'm throwing the ball well. I'm not worried about stat line."
By no means did Romo struggle last season, although he did record his highest ERA (2.54) since 2009. He recorded 38 saves and posted a 1.08 WHIP.
But Romo was flat-out dominant from 2010-12, and he's hopeful that adding another trusted pitch to his repertoire will help him get back to that level in '14.
"That's the reason why I'm trying to use it -- so that I can be more of a complete pitcher," Romo said. "It's not so that I can use it more, but so that I have it, so that when I do need it, I can go to it."
AJ Cassavell is a reporter for MLB.com. Follow him on Twitter @ajcassavell. This story was not subject to the approval of Major League Baseball or its clubs.