SCOTTSDALE, Ariz. -- Pitchers and catchers began working out for the first time Monday at Salt River Fields, but already it seems the Opening Day pitching staff is pretty well set.

Well, at least on paper.

D-backs GM Kevin Towers and manager Kirk Gibson are well aware of the perception, and they will do the best they can to not let it permeate the clubhouse.

"The last thing we want to do is send a message that they've got no chance," Towers said.

"When it's done, we're going to take 25 guys," Gibson said, referring to the end of Spring Training. "But history will tell that there's going to be more than 25 guys that we're going to need to get to where we want to go."

Much can happen between now and the April 6 opener against the Giants. Anything from injuries to unexpected struggles, but here's where the staff looks like right now:

Starting Rotation

Locks: Ian Kennedy, Daniel Hudson, Trevor Cahill and Joe Saunders
Almost a lock: Josh Collmenter
Summary: It's hard to imagine that Collmenter could lose his spot after the way he performed for the team last year, and it would seem he would have to really have a disastrous spring in order to not be in the rotation.

Spring Training
• Spring Training schedule

Keep an eye on young pitchers like Trevor Bauer, Tyler Skaggs, Wade Miley, Patrick Corbin and Charles Brewer. One of the reasons the D-backs chose to re-sign Saunders was so that they could take their time with their young hurlers. A good spring by that group would cement their standing in the organization's eyes while also making a case for an in-season callup. In addition, keep an eye on Barry Enright. Gibson loves his work ethic and athleticism and a good spring could set him up for a callup as well.

Bullpen

Locks: J.J. Putz, David Hernandez, Brad Ziegler, Craig Breslow, Takashi Saito
Almost locks: Joe Paterson and Bryan Shaw
Summary: The performances by Paterson and Shaw last year almost certainly have earned them a spot in the 'pen. Like Collmenter, they would need to have an unexpectedly awful spring to not find themselves on the Opening Day roster.

It's worth noting that Saito is 42 years old and has had a history of injury problems. Plus, bullpen performances can vary wildly from year to year, so it's notoriously hard to predict. Towers has said that Jonathan Albaladejo and Joe Martinez bear watching, and there are a wide range of others, like Sam Demel and Mike Zagurski, who also could make a push, not to mention one of the starters sliding over to the 'pen.

"We're not giving out jobs here," Towers emphasized. "You have to earn it."