Burnett, on the other hand, sports a 3.06 ERA in 38 games for the Pirates and was equally effective against both sides of the plate. Opposing left-handers are hitting .189 against the 26-year-old this year, while right-handed bats are hitting at a .211 clip.
Based on games like Monday night -- when Olsen pitched seven innings of two-run ball but Ron Villone and Julian Tavarez gave the Marlins the win thereafter -- it's the kind of help the Nationals bullpen can certainly use.
Heading into Tuesday's game, Washington's relievers are a combined 7-25 with a 5.67 ERA, which ranks last in the Major Leagues.
But, before Monday's setback, players felt things were starting to turn around.
"At the start of the season, we might not have had the right guys," said left-hander Joe Beimel, who sports a 3.56 ERA in 33 games. "[Acting general manager] Mike Rizzo has done a good job of switching it over and getting some guys in here who are able to go out there and throw up some zeroes, pitch well in crucial situations, and I think, as a whole, we've kind of turned it around this last month or so."
From June 17-20, the 'pen gave up just one run in 13 2/3 innings. But in the last eight games, Nats relievers have combined to give up 21 runs in the last 21 innings -- an ERA of 9.00. In June, the relievers have posted a 5.37 ERA -- only a slight improvement over April (5.40) and May (6.11).
But Rizzo remains optimistic.
"I've seen it get better, and been better than we've had form the start of the season," Rizzo said. "I think people have found a little bit of a comfort level and a bit of a niche. I think that's helped. Of course, consistency has been an issue, and I think Burnett will help stabilize that bullpen this year."
Manager Manny Acta said he expects Burnett -- the third southpaw in the 'pen -- to work in middle relief and said he'll be more than just a situational lefty.
The Nats are hoping he'll help prevent more nights like Monday.
"[The bullpen has] only stumbled a couple of times, and they really picked it up," lefty starter John Lannan said. "It's part of the game, you know? Sometimes, things are just going to happen. That ball that Wes Helms hit down the line [to lead off the eighth inning] was right on the line. Just stuck his bat out, and stuff like that is going to happen.
"We've got some guys who have been around and they know what they're doing. I think they can bounce back pretty quick."