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6/22/2013 4:06 A.M. ET

Delgado to start as part of four-man rotation

PHOENIX -- The D-backs made it official: Randall Delgado will get the start Sunday in the series finale with the Reds.

The right-hander started in place of the injured Brandon McCarthy on Tuesday and held the Marlins to two runs over seven innings.

Most important to the D-backs' decision-makers was that Delgado, who battled for the No. 5 spot in the rotation this spring, did not allow a walk.

With right-hander Ian Kennedy serving a 10-game suspension, the D-backs are using a four-man rotation. The team can do that because it had Thursday off and has another off-day Monday.

Kennedy is eligible to return next Saturday, so the D-backs will need Delgado or another pitcher to start next Friday against the Braves in Atlanta.

Spruill called up to spell Collmenter in relief

PHOENIX -- With long reliever Josh Collmenter unable to pitch for a few days after throwing six innings of relief Wednesday, the D-backs promoted Zeke Spruill from Triple-A Reno.

Spruill entered Friday's 11-5 win over the Reds in the sixth inning, allowing one hit with one strikeout for a scoreless inning in his Major League debut.

Collmenter was forced into action in the second inning when Trevor Cahill left after being hit in the right hip with a line drive.

"We used Collmenter the other day, so he's not available today," D-backs manager Kirk Gibson said before Friday's game. "We were uncomfortable with that, so we got Spruill up here."

Spruill started the year in Double-A Mobile but was quickly promoted to Reno, where he is 3-3 with a 4.06 ERA in nine starts.

In his last two starts for Reno, he tossed 17 scoreless innings.

"He's throwing the ball great," Gibson said. "Kind of keeps the ball down, good sinker, he's got a split, a little slider."

To make room on the 25-man roster, the D-backs designated infielder Josh Wilson for assignment.

With Collmenter likely able to pitch again in a couple of days, it seems Spruill's stay will be a short one, and the team could activate second baseman Aaron Hill on Sunday or Tuesday to take Spruill's place.

Spruill, the D-backs' No. 8 prospect according to MLB.com, got the nod over top prospect Tyler Skaggs, largely because of the role he would be filling.

"I think we see Spruill better out of the bullpen, and there was less comfort with Skaggs coming out of the bullpen," Gibson said.

Spruill was acquired in January as part of the deal that sent Justin Upton to Atlanta.

Snake bites

• Gibson said Hill would need at least two more games on his rehab assignment before being activated.

Hill is scheduled to play Friday and Saturday for Triple-A Reno.

• Injured closer J.J. Putz was scheduled to pitch for Reno on Friday night. Putz may take a day or two off before the team has him pitch in back-to-back games.

"J.J.'s pushing," Gibson said. "He's ready in his mind."

Gibson declined to say whether Putz or Heath Bell would close when Putz returned.

"I haven't determined that yet," Gibson said. "We want to see how he's throwing, see where we're at."

• Outfielder Adam Eaton, who is on the disabled list with a strained left elbow, could head out on a rehab assignment to serve as a designated hitter as soon as Thursday.

Eaton could begin playing in the field as soon July 6 if all goes well.

• McCarthy, who is on the DL with shoulder inflammation, threw a 25-pitch bullpen session Friday and is slated to throw another Monday.

• Gibson discussed some of his criteria for when players are ready to come back from injury rehab assignments.

"I want them to be comfortable, I want them to be healthy, strong, and I want to have them up to speed," Gibson said. "It's not the AZ Summer League, it's not Double-A, it's not Triple-A; it's pretty competitive, so we want to make sure we prepare those guys to be ready to succeed."

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.