Trying for a fifth consecutive victory overall, the Pirates look to complete their latest home sweep by handing the Marlins a fifth straight defeat Sunday.
Pittsburgh (53-40) had dropped six straight at home to Miami before holding on for a 4-3 victory Friday and winning 5-1 on Saturday for its 15th victory in 20 games overall.
The Pirates, one-half game behind first-place Cincinnati in the NL Central, have won four in a row and 20 of 24 at PNC Park where they are a major league-best 31-14 and have swept three series.
Miami (44-50), meanwhile, has totaled seven runs while losing four straight after opening its six-game trip with a 9-5 win at Chicago on Tuesday. The Marlins have lost 12 of their last 16 away from home.
Manager Ozzie Guillen was asked where his frustration level is, sitting 10 games back in the NL East.
''Mine? I don't know, I showered before you guys (in the media) got here, let's put it that way,'' he said. ''I never did that before in life (during the regular season). I made sure I cooled off before I talked to you guys.''
A.J. Burnett threw 7 2-3 strong innings to remain defeated at home while Garrett Jones had two RBIs on Saturday. The Pirates scored four times in the fourth inning when they did not record a hit and benefited from four walks, two hit batters and an error.
It's the first time a team scored four runs in one inning without a hit since Oakland did it on Sept. 23, 1998.
"That's the game of baseball, man," said Burnett, who is 7-0 with a 2.00 ERA in 10 home starts this season. "That's why we play.''
Pittsburgh center fielder Andrew McCutchen went 1 for 4, but still leads the majors with a .371 batting average. The All-Star is 5 for 13 (.385) against the Marlins this season.
Scheduled Pirates starter Jeff Karstens (2-2, 4.15 ERA) is 2-0 with a 2.45 ERA in his last three starts, walking five and striking out 19. After giving up two runs over his previous two outings, the right-hander yielded four in seven innings of a 5-4 loss at Colorado on Monday.
"I know I can get guys out, against anybody," Karstens told the Pirates' official website. "It's just a matter of making pitches; the frustration is when I know the pitch I want to throw, and don't execute it, and they end up getting hits that play into a bigger inning."
He is making his first appearance against the Marlins since a relief outing in 2010, and first start since he gave up a run in six innings of a 3-2 win April 21, 2009.
Justin Ruggiano, who has never faced Karstens, homered Saturday for the Marlins. The outfielder is batting .364 with seven home runs and 18 RBIs in 40 games since Miami acquired him in a trade with Houston on May 26.
Anibal Sanchez (5-6, 3.95), who has allowed three earned runs in his last two starts, hopes to help the Marlins avoid the sweep. He yielded two runs - one earned - and struck out seven against the Cubs on Tuesday.
The right-hander gave up three runs in seven innings of a 3-2 home loss May 14 to fall to 2-2 with a 2.17 ERA against the Pirates.
Pittsburgh's Rod Barajas is 5 for 10 with two homers and three doubles against Sanchez.