Ian Kennedy, who had already been announced as the Opening Day starter, will be followed by Daniel Hudson, Josh Collmenter, Trevor Cahill and Joe Saunders.
Most had assumed that Collmenter would fill the No. 5 spot in the rotation rather than Saunders.
"I'm just happy to be a part of it," Collmenter said.
Gibson did not reveal the exact reasoning behind the way he set up the order.
"We obviously put a lot of thought into it," Gibson said. "We looked at peripherals as well, where our season's going to start, where guys are at, and this is the decision we came up with."
The only reason pitching in the No. 5 spot can sometimes be an issue is if a team chooses to skip his turn when there is an off-day in the schedule to keep the other four starters on a regular schedule.
The D-backs, though, say they will not skip starters during the season and therefore the No. 5 distinction doesn't matter.
"I think Cahill was a No. 1 last year and he's No. 4, [but] we don't look at it that way," Gibson said. "We don't skip starts. Everybody is going to get their starts, everybody's going to get their 33 starts at least and get an opportunity. This is the way we're going to start the season."
One of the reasons Gibson prefers to give his starters an extra day is he expects them to pitch deep into games, so he prefers they get additional rest.
"You can look at the numbers what they do on four days' rest, five days' rest, six days' rest, etc.," Gibson said. "I think we just look at the bigger picture, though, at the cumulative effect on the year."
Collmenter struggled in his first three spring outings and also battled a case of forearm stiffness that caused him to miss a start. Gibson, though, was steadfast in his support of Collmenter in large part because of the contributions he made in 2011 when he was 10-10 with a 3.38 ERA. The right-hander also came up big in the National League Division Series with his performance in a must-win Game 3.
Collmenter looked better in his start Sunday against the Padres.
"He threw the ball well, saw more movement on his ball, and that tells us his arm slot is more where it was in the past," Gibson said. "He threw the ball down, threw it up when he wanted, his changeup was better, more effective. It was a good start for him yesterday, so we're confident in what he's going to do."
Kennedy, Hudson and Collmenter will face the Giants in the season-opening series, while Cahill, Saunders and Kennedy will face the Padres in San Diego.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.