Karstens was making his first Major League start this season. A diminished offense would be without two of its previously most-feared hitters in Bay and Xavier Nady. The back end of the bullpen could no longer count on Damaso Marte.
And then there was the fact that the Cubs were riding a five-game winning streak, which included four straight against the division-rival Brewers.
"Going into it without a Jason Bay or an Xavier Nady, the morale is a little bit down," shortstop Jack Wilson said afterward. "Obviously, it's a different clubhouse atmosphere. But when you get the younger guys and they come in and play right away, that does make a difference. Now you're turning your attention to these new guys and what they can do. That turns your attention from not thinking about the guys we are missing."
If that's the case, then let this restructured club begin forging its own stamp.
The standout on Friday was Karstens, if for nothing more than the fact that quality starts from someone other than Paul Maholm have been few and far between recently. The right-hander, who was acquired on Saturday as part of the deal that sent Nady and Marte to New York, pitched six shutout innings.
Coming into the start, Karstens' appearances this season had been limited to 12 Triple-A starts. If first impressions are as lasting as they are said to be, the 25-year-old right-hander already made his mark.
"It's tough to go to a new team," said outfielder Jason Michaels, whose two RBIs led the offensive attack. "All these guys, you don't really know what's going on. Karstens came in and did a great job."
Karstens limited the NL's best offense to five hits and four walks in his six innings.
"They haven't seen me," said Karstens. "I haven't seen them. So they basically had no idea how I was going to attack them."
His plan of attack was quickly evident. A Chicago club that thrives on fastballs saw very few from the Pittsburgh righty, who relied heavily on his slider and changeup early.
"He changed speeds very well," manager John Russell said. "He started to throw some more fastballs later to help keep them off-balance. He's got some weapons to pitch with."
Evident by the lack of production, the Cubs, too, seemed to be caught off guard by Karstens' pitch repertoire.
"He pitched a great game," Chicago outfielder Jim Edmonds said. "We'd never seen him, we didn't have much footage, and from what we saw, he definitely looked better than what we saw on video. I can't say 100 percent that we didn't have a letdown, but you have to give that kid credit. He deserves it."
Offensively, it was Michaels and Wilson who led the way. Back-to-back second-inning singles by both veterans pushed the Pirates out to an early 2-0 lead. Michaels then added his sixth home run on the season with a two-out solo shot in the sixth to pad the cushion.
It was, as Wilson said, the beginning of some of the veteran players stepping forward in order that new clubhouse leaders emerge.
"We have new guys in our clubhouse," the shortstop said. "Get to know them. Have fun. Help them with the big league level. There's a lot of work to be done to help these guys hopefully take the next step."
Both new guys -- Brandon Moss and Andy LaRoche -- made their first starts for the Pirates, despite not arriving in Chicago until Friday morning. Moss went hitless in three at-bats and drew a walk. LaRoche singled and scored a run in his first at-bat before being retired in his next three.
Defensively, however, both impressed. LaRoche keyed a game-ending double play, while Moss made a handful of tough plays in right, including doubling the Cubs' Kosuke Fukudome off first base and making a catch after losing the ball in the sun momentarily.
"It's nice energy to see from those guys," Russell said. "You can tell they're excited to be here and also it gives you an idea of what they're capable of doing. It's fun to see."
And in the meantime, the bullpen keeps plugging along, even without Marte. Denny Bautista made yet another scoreless appearance, as he has now allowed just one run in nine innings since the All-Star break. Sean Burnett, who continues to be called upon late in games, induced a critical inning-ending double play in the eighth. And John Grabow was the closer du jour, as he picked up his first save of the season and third of his career.
It was the type of team effort the club needed in order to start moving forward rather than lamenting what's already been done.
"There's going to have to be people who step up," center fielder Nate McLouth said. "It's just going to take a lot of contributions from everybody. They're certainly missed. I guess we'll see who rises to the challenge."