CHICAGO -- The D-backs bullpen has been far too generous this year for manager A.J. Hinch's liking.

Heading into Saturday, Arizona relievers have walked 38 batters this year, an average of five per nine innings, second-worst in the National League.

"The walks out of our bullpen are killing us," Hinch said. "To me it's more of an approach. Guys start pitching away from contact. It's a timid way to approach the hitter. They're coming in with generally the game on the line and game-changing-type at-bats and it takes a lot of conviction to pound the strike zone. But that's what the good bullpens do. They allow contact on the ground, they pitch with an aggressiveness that is necessary to get through that."

One example of the bullpen's struggles in that area came Friday when Blaine Boyer walked three in one-third of an inning, one of which forced in a run. Aaron Heilman then came on in relief and he walked in a run before getting out of the inning.

"It's a rut that we can get out of," Hinch said. "We should be a contact-based bullpen. I think they can throw strikes, my concern is whether or not they have the conviction to make pitches. The easiest thing to do is to try to pitch around that contact and get them to maybe get themselves out, but it's a tough league to do that in."

Bases-loaded walks have been an issue for the pitching staff as a whole this year as it entered Saturday having walked a league-high seven with the sacks full.

Rosales to have surgery on right foot

CHICAGO -- D-backs reliever Leo Rosales was diagnosed with a stress fracture in his right foot on Saturday, which will require surgery.

The injury could keep the right-hander out of action for at least two months.

Rosales first felt discomfort in the ankle on April 18, when he got the Padres' Kyle Blanks to ground into a double play. At the time, Rosales was pitching well and didn't want to go on the disabled list.

Instead, Rosales had the ankle wrapped by the training staff and tried to continue to pitch.

"He was getting better, but then he took a step back [Wednesday]," said D-backs manager A.J. Hinch, referring to pain Rosales felt during his outing against the Rockies.

The D-backs placed Rosales on the DL on Thursday.

Hinch shakes up lineup

CHICAGO -- The D-backs lineup had a little different look to it Saturday afternoon.

Normally, manager A.J. Hinch puts Stephen Drew in the No. 2 hole, with Justin Upton right behind him. On Saturday he reversed the pair.

The thinking behind the move was to split up the left-handed-hitting leadoff man Kelly Johnson and Drew after watching Cubs southpaw John Grabow mow through the pair in the seventh inning. Chicago has three lefties in its bullpen.

"We'll give them a different look today and put Upton in [between] them and see if they want to go left-right-left [or] do they want to leave the lefties in to face Justin?" Hinch said. "Makes them a little difficult on them to decide what to do later in the game."