"These guys have to show us that they're more important than a last righty that's a power guy," Hale said of his left-handed candidates.
Lefties still in camp include Matt Reynolds, Keith Hessler and Wesley Wright. Reynolds has been out of action recently due to tightness in his back and has a 5.40 ERA, while Hessler has a 6.75 ERA. Wright has the best numbers of the trio with a 1.42 ERA.
Five right-handers, though, have put up dominating numbers:
• Evan Marshall, who nearly died last August when he was struck in the head by a line drive while with Triple-A Reno, has allowed one unearned run in seven innings. He was outstanding for the D-backs in 2014 before struggling after making last year's Opening Day roster.
• Jake Barrett has allowed one earned run over six innings. He split time between Double-A Mobile and Reno last season.
• Enrique Burgos, who appeared in 30 games with the D-backs last year, has allowed one earned run over five innings. On Saturday night, he flashed an impressive split-finger fastball, which the team has been encouraging him to throw more.
• Silvino Bracho, who started last year with Class A Advanced Visalia and finished it in the big leagues, was set back by a groin issue early in camp, but he has not allowed a run in either of the two Cactus League games in which he's pitched.
• Kaleb Fleck, a non-roster invitee, has taken some mechanical adjustments made before camp started and run with them. He has thrown three scoreless innings in Cactus League games and has also impressed in "B" games.
"If we're going to go with a second lefty, that door is wide open," Hale said. "Those righties are starting to close the door a little bit on the second lefty."
All of the right-handers have Minor League options, which will come in handy because teams always need bullpen reinforcements during the season.
It also gives the D-backs the ability to send a reliever down to the Minors to rest if he has thrown several days in a row.
"We'll start with seven and might end up needing 20 [with] injuries, and just guys get tired," Hale said.
Steve Gilbert is a reporter for MLB.com. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.