PHOENIX -- As pitching injuries and ineffectiveness took their toll on the D-backs' starting rotation last year, Arizona dipped into every bit of its organizational pitching depth.

It was a great opportunity for Alex Young and Taylor Clarke to gain big league experience, and it also reinforced an old baseball maxim: You can never have too much pitching.

That’s worth keeping in mind, because with the signing of free-agent lefty Madison Bumgarner and the decision to hang onto Robbie Ray, the D-backs have more starting pitchers than they have spots in the rotation.

It's a good problem to have, and while there could be a battle for the No. 5 spot, keep an eye on what happens to those who don’t make the rotation. Who will shift to the bullpen, and who will end up as insurance in the Triple-A Reno rotation?

After Bumgarner and Ray, right-handers Luke Weaver -- provided he’s healthy -- and Mike Leake figure to have spots sewn up heading into camp.

That leaves the No. 5 spot technically open, but the organization is known to think extremely highly of right-hander Zac Gallen, who was acquired from the Marlins at the Trade Deadline. He would seem to be the heavy frontrunner, though the team will push the idea of competition at camp.

In eight starts for the D-backs, Gallen posted a 2.89 ERA, and at times, he was dominant. He held the Phillies to one hit over five innings in his Arizona debut on Aug. 7, and he allowed just one hit to the Padres over seven innings on Sept. 4.

“Of course I would have to say that he's going to get some very, very strong consideration, considering that he came on board and pitched some really big games for us,” D-backs manager Torey Lovullo said.

Gallen posted a 2.5 WAR, per Baseball-Reference, including his time with the Marlins -- just narrowly behind the 2.8 bWAR posted by Bumgarner last year.

If Gallen does indeed claim that spot, it likely means a move to the bullpen for right-hander Merrill Kelly. Signed out of Korea prior to last season, Kelly can’t be sent to the Minors without his permission. The 31-year-old was the only member of the Arizona rotation to not miss a start last year, as he went 13-14 with a 4.42 ERA in 32 trips to the mound.

Then there’s Young, another rookie, who was pressed into service at the big league level last year. In 17 games (15 starts) he had a 3.56 ERA and a 125 ERA+.

Young started 2019 in the Triple-A Reno bullpen in part because the organization wanted to give him a couple of different avenues to reach the big leagues. With his experience relieving, the 26-year-old could be shifted to the bullpen if he doesn’t make the rotation, which would give Arizona a second lefty to go along with Andrew Chafin.

Clarke and Jon Duplantier each had varying degrees of success during their time in the big leagues, and prospect Taylor Widener is still highly regarded in the organization despite a tough 2019 season in Reno.

And there’s also veteran Edwin Jackson, who was recently signed to a Minor League deal and invited to big league camp.

While Gallen is certainly a frontrunner, the D-backs will no doubt continue to emphasize that there’s going to be plenty of competition. That’s an organizational philosophy they have hammered home under Lovullo, who believes that it brings out the best in players.

“We're seven, eight, nine deep, and all those guys are going to get some strong consideration,” Lovullo said. “And they're going to be told where they stand when they come to Spring Training. I know that they're going to be ready to go, ready for the challenge.”