Wasdin joins right-handers Salomon Torres, Matt Capps, Shawn Chacon and Jonah Bayliss in the bullpen, and lefties Damaso Marte and Juan Perez as the relief situation was set on Friday.
John Grabow, another left-hander, will begin the season on the 15-day disabled list, retroactive to March 23.
Among other roster moves, the Pirates released right-hander Dan Kolb, outfielder Luis Matos and infielder Jose Hernandez. Pittsburgh purchased Wasdin's Minor League contract, and also infielder Don Kelly's.
General manager Dave Littlefield said the decision to keep Kelly, a 27-year-old Pittsburgh native who reached Triple-A in the Tigers' farm system before signing with the Pirates, was based on a combination of performance and versatility.
"I think as we look at the mix of the people on the bench ... Donny Kelly's had a fantastic camp," Littlefield said. "He hits left-handed, there's some versatility, and as you look at the mix of the people that we were getting closer to having on the bench, we felt that Kelly was the better fit."
Pittsburgh still has one roster move left to make before Sunday's 3 p.m. ET deadline. As of now, it appears the battle for the final spot has come down to first baseman Brad Eldred, who has been on a tear this spring with a .311 average (19-for-61) and team highs of seven doubles, six homers, 13 RBIs and 11 walks as of Friday, and outfielder Nate McLouth, who was up with Pittsburgh all of last season.
What will Freddy do? While most questions have been answered this spring, where National League batting champion Freddy Sanchez will be on Opening Day remains a mystery. The 29-year-old has competed in three games so far, but it's unclear whether he'll gain enough at-bats by Saturday to feel comfortable taking the field in Houston on April 2.
Littlefield didn't comment either way on what he expected, only that there were three options: Sanchez on the disabled list, Sanchez playing off the bench or Sanchez starting. Littlefield set the deadline for Saturday morning.
Record-breaker: Friday afternoon's crowd of 4,419 broke a McKechnie Field record for most fans drawn there in the Grapefruit League season since the team moved its headquarters to Bradenton in 1969. In all, 81,967 fans attended Pirates home games this spring, an average of 4,971 people for each of 16 games. Seven of those games were sellouts.
"The fan support throughout Spring Training has been tremendous," said Pirates CEO Kevin McClatchy. "We want to thank everyone in Bradenton for a great spring and look forward to coming back for many years to come."
Up next: Pittsburgh travels to Fort Myers on Saturday for its final Grapefruit League game. Left-hander Paul Maholm will start for the Pirates against Minnesota righty Sidney Ponson. First pitch is scheduled for 1:05 p.m. ET.