"We've got the magic number down to six, and these guys know it," manager Dale Sveum said. "They've got a lot of pride to stay away from that [100-loss] number. They battled to win, whatever, six out of seven to put us in a situation to do that. A week ago, it wasn't looking too good."
A week ago, the Cubs had lost six in a row. Pittsburgh is fighting to stay alive in the National League Wild Card race.
"They're playing for their lives right now," Sveum said of the Pirates, who were 3 1/2 games back in the Wild Card standings at the start of the night's games. "Every game to them is a playoff game, and every game to us is a playoff game in our players' minds, because they're talking about staying away from 100 losses."
It makes it easier when players like Castro show how much they've grown in just a couple of at-bats. Castro hit a RBI single in the third off James McDonald (12-8), who then walked the bases loaded with two outs in the fourth and was lifted for lefty Justin Wilson. Rizzo greeted him with his double to open a 3-0 lead.
"I walked three guys in an eventual big inning," McDonald said. "Walks aren't acceptable. I had two outs, I should have got that out and been in the dugout."
Alfonso Soriano then hit a RBI single off Chris Leroux to make it 4-0 and notch his 97th RBI of the season.
Pedro Alvarez hit a RBI single in the Pirates' fifth, and they added two more runs in the sixth to close to within a run at 4-3.
The Cubs had one on and two outs when Jared Hughes took over in the sixth. His first pitch hit Soriano, and Castro launched the next pitch into the left-field bleachers to extend Chicago's lead to 7-3. But Castro's at-bat was key not just because of the cushion but because he recognized that he needed to alter his stance.
"That's one of the best guys out of the bullpen," Castro said of Hughes. "He throws a sinker, and the ball moves down hard. That's why I was ready at home plate. I said, 'I don't want to do a leg kick because I don't want to be late.' So I did one step and swung the bat."
Sveum has suggested more than once that Castro needs to get rid of the leg kick.
"Those are the kind of things you're looking for, to see guys making adjustments from pitcher to pitcher," Sveum said. "That's when you start to grow as a player, when you start doing those kind of things."
Castro, who led the NL in hits last season, isn't about to give up his kick totally.
"If a guy is nasty, I [don't use the leg kick]," Castro said. "I do that with [Aroldis] Chapman, too. If you do a leg kick, you don't have a chance with a guy who throws 98 [mph]. [Hughes] doesn't throw 98, but he throws 94 and it's nasty."
Castro has posted .300 batting averages in his first two seasons in the big leagues. He's sticking with what's comfortable.
"I've been doing my leg kick all my life," he said. "I got 200 hits last year with the leg kick. I know it can work, but I don't want to be thinking too much."
Rusin (1-2) gave up two runs on four hits over five-plus innings, striking out a personal-high six batters in his fourth start. The lefty didn't give up a hit until the fifth and was able to strike out Andrew McCutchen twice.
What's it been like, pitching in the big leagues?
"Crazy," Rusin said, still chilled after his celebratory beer shower. "I don't think it's hit me yet. It'll hit me in the offseason when I've had time to think about it. Right now I'm pretending I'm still in Triple-A and doing what I do."