With starter Chien-Ming Wang on the disabled list, Traber was called up before Tuesday's series opener against the Padres, making him the only left-hander in the bullpen and the lone southpaw reliever the Yankees have had this season.
This time, though, he has a slider, something he's never had before.
"I went down there, and one of the main things I worked on was learning how to throw a slider, a hard-in pitch," Traber said. "If I could get something that was hard-in, I figured I could get another look."
The learning process was an uphill battle.
"It was supposed to be easy," Traber said. "It was [tough]. I got hit around pretty well for a good month. It was tough to figure it out, because it wasn't really a pitch I ever threw and I wasn't sure if I wanted to. But through talks and to make yourself into a better pitcher, sometimes you have to find something else."
Through his eight innings with the Yankees entering Tuesday, Traber has a 4.50 ERA and has yielded four runs. In 24 1/3 innings for Triple-A Scranton this season, Traber was 2-0 with a 4.07 ERA and 25 strikeouts.
In the Minors, Traber wasn't used exclusively against left-handed hitters. The Yankees are looking at him as particularly useful during their six-game homestand against San Diego and Cincinnati.
"We've talked about a left-hander," manager Joe Girardi said. "We're going to face some clubs that have left-handers. You're looking at the Padres. They have a couple: [Brian] Giles and [Adrian] Gonzalez in the middle of the order. You're looking at the Reds. They have a bunch. I think it's an opportunity, if the situation presents itself, for Billy to help us out."
Willie Bans is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.