But the bigger reason is that general manager Josh Byrnes and the D-backs' front office believes in the core of this team.
"There are a lot of components there that we think are real positives," Byrnes said. "I think a lot of the pieces to get back to winning are already in place."
Outfielders Justin Upton, Chris Young, Gerardo Parra and Conor Jackson, along with third baseman Mark Reynolds, shortstop Stephen Drew and catcher Miguel Montero form a group of players the D-backs can build around.
"We got really good performances from players in the age range from 21 to 26," Byrnes said. "A guy like Parra has gotten to the big leagues, Montero has gotten more playing time."
The Pena trade brought another possible piece in first baseman Brandon Allen, who has been tearing it up at Triple-A Reno since being acquired.
On the pitching side of things, Dan Haren is locked up long term and Max Scherzer certainly figures to be a key part of the rotation going forward. Depending on the health of Brandon Webb, he could give the D-backs a solid front three.
In the bullpen, closer Chad Qualls will return and young pitchers Juan Gutierrez, Esmerling Vasquez and Clay Zavada have shown promise while veteran Jon Rauch has improved as the year has gone on.
The D-backs probably could have dealt veteran starters Doug Davis and Jon Garland, both of whom can be free agents in the offseason, but they did not just want to give them away, because for the D-backs, there is still much to play for in the season's final two months.
"The good part about being quiet during the Deadline is that the veteran pitchers like Jon Garland and Doug Davis can help us get our swagger back," manager A.J. Hinch said. "They can help us get our momentum back. One of the things that we want to do is provide a winning environment, a winning culture in the clubhouse and on the field."
Sure, they have long been out of the playoff hunt, but a strong finish would go a long way toward accomplishing some of the goals Hinch has set for them and give the organization a better feel about an otherwise dismal season.
"The rest of this season, there is plenty of time to see progress and improvement," Hinch said. "And if we've learned anything, we've learned that when we're good, we're pretty good and when we're bad, we can implode to the point of not even recognizing ourselves. We have to push back toward winning ways, which we've gotten away from."
The D-backs took a step in that direction during the month of July when they posted a winning record at 14-12.
"I think our offense is starting to look like a better offense," Byrnes said. "Our pitching, even without Brandon Webb, I think we still lead the league in road ERA. Our starting pitching has still been good, our bullpen has been inconsistent, but shown flashes."
There will plenty of work for Byrnes and his staff this winter with some big decisions looming.
The biggest will be what to do about Webb's $8.5 million option for next season. Depending on how that shakes out, the club will be looking for one or two starting pitchers with top prospect Jarrod Parker expected to compete for a spot in the rotation next spring.
The hole at second base will need to be addressed and with Montero getting the bulk of the time behind the plate, the team could use catcher Chris Snyder as a trade chip to help fill in the gaps.
The core, though, will remain the same.
"This is the same core of players that had success in 2007 and reached the National League Championship Series," Hinch said. "So there's no reason to believe that this core group can't withstand a tumultuous season and end up on our feet challenging for better days."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.