They're only halfway to the finish line, but the Pittsburgh Pirates' regular season could turn into something special.
The Houston Astros' season is falling apart.Pittsburgh goes for its first four-game sweep in six seasons Thursday night at PNC Park, where the Astros will try to avoid a season high-tying eighth consecutive loss in their first contest since Carlos Lee was traded.The NL Central-leading Pirates (45-36) have rallied in each of the first three games of this series to reach the midpoint of 2012 at a season-best nine games above .500. It's the first time the club has been this far above the break-even point since it won its third consecutive NL East title in 1992.That was also the last time the Pirates went to the playoffs."The depth of it, I don't think our guys can understand because they haven't embraced it the last 19 years," manager Clint Hurdle, whose team has won 15 of 18 at home, told the Pirates' official website before Wednesday's 6-4 victory. "So I don't think we can understand the impact we can make. But giving (the city) a competitive team, a team they can be proud of, yes, I do think they get that."The Pirates are definitely pleased with their .337 batting average and 8.3 runs per game during a 7-1 run."We knew the bats were going to start coming around, and when we did we knew we were going to score a lot of runs," second baseman Neil Walker said.They could continue that surge if Andrew McCutchen, the majors' leading hitter at .360, and Pedro Alvarez can stay hot. McCutchen is batting .514 (18 for 35) with three homers and eight RBIs in his last eight contests, while Alvarez is hitting .412 (7 for 17) with two home runs and 13 RBIs in his last six.That type of production could benefit Jeff Karstens (1-2, 5.25 ERA), who will try to lead the Pirates to their first four-game sweep since May 29-June 1, 2006, against Milwaukee.In his second start since missing more than two months with right shoulder inflammation, Karstens struck out a season-best seven in seven innings of Saturday's 7-3 victory at St. Louis. It was the right-hander's first win since Aug. 10, 2011, at San Francisco.Karstens gets his first look at the Astros (32-50) this season after posting a 0.40 ERA while winning all three starts against them in 2011.He'll face a Houston club trying to avoid a winless seven-game trip and its first 10-game road skid since an 11-game stretch April 16-May 8, 2005."Obviously, we didn't get the results we'd like to have gotten," manager Brad Mills told the Astros' official website after his team fell a season-worst 18 games below .500.Houston will now move on without Lee after he was traded to Miami on Wednesday for prospects Matt Dominguez and Rob Rasmussen. The Astros will likely call up Brett Wallace from Triple-A Oklahoma City to replace Lee.Bud Norris (5-5, 4.90) gets the ball for Houston after losing a career-high fourth consecutive start on Friday, 4-0 at the Chicago Cubs. It was the right-hander's first appearance in 17 days following a stint on the disabled list with a sprained knee.Norris struck out eight in six innings of a 1-0 victory at Pittsburgh on May 11. The Pirates have won the last five versus Houston -- all at PNC -- since that first meeting of 2012.