Winless in his last five starts, all in August, Cahill has gone 0-2 with a 5.14 ERA over that span.
His worst start of the month came on Sunday against the Padres, allowing four runs on eight hits in just 3 2/3 innings for the loss. Although Cahill (9-11, 3.99 ERA) struck out six, it marked his shortest outing in more than a year.
However, he'll try to end the month on a good note and get that coveted win when the D-backs face the Dodgers on Friday at Chavez Ravine. Arizona, which snapped a six-game losing streak in Thursday's opener, has won seven straight over Los Angeles.
"It was not good, he was unable to locate the ball when he needed to make a pitch," Arizona manager Kirk Gibson said of Cahill's last start. "Trevor just didn't have a good performance. He's very inconsistent with where he wants to throw the ball."
Meanwhile, right-hander Aaron Harang will take the hill looking for his 10th win of the season for the Dodgers, who have fallen 4 1/2 games behind the Giants in the National League West. If he can get the victory, it would mark the sixth time in his career that he's reached the feat.
Harang lasted 5 1/3 innings on Sunday against the Marlins, allowing three runs on six hits for the loss. He also struck out four and walked one, falling to 9-8 on the season with a 3.70 ERA.
The difference in the game came on two home runs. Harang surrendered a solo shot to Giancarlo Stanton in the fourth inning and a two-run home run to Rob Brantly in the fifth.
D-backs: Bloomquist nearing return
While shortstop Willie Bloomquist (back) could be activated on Saturday when rosters expand, how much he initially plays is still uncertain.
After playing consecutive games, Bloomquist seemed to stiffen up, so the D-backs will be cautious with him.
"When we bring him up and play him for a game do we have to sit him for a game?" Gibson said. "Probably initially we couldn't play him multiple games. Probably no risk in activating, but he's got to be able to play. You don't want to just activate him and not be able to play him."
Dodgers: Billingsley gets plasma injection
Starting pitcher Chad Billingsley had a platelet-rich plasma injection in his injured right elbow on Thursday.
The injection is used for tears in tendons and ligaments and something that several Dodgers pitchers have used to speed up the healing process while delaying surgery.
The Dodgers have not said whether Billingsley has a tear in his elbow, although he did have an MRI last weekend that would have revealed a tear.
"If he's able to throw after this, he's not finished and if that's the case, he'll start a throwing program," manager Don Mattingly said. "If not, there's a different plan. We're trying to see if this helps. It could be something that ends up more than that."
Matt Kemp was out of the Dodgers' starting lineup Thursday night against the D-backs because of a stiff left shoulder, a delayed symptom from running into the fence on Tuesday at Coors Field.
"His knee feels pretty good, doing a lot more stuff, but his left shoulder is a little stiff and that's keeping him back today," Mattingly said. "I did the lineup tonight thinking he still had a chance to play. He did a lot to get loose and a lot of areas are really good. But the left shoulder didn't get loose."
Adrian Gonzalez, wearing his new Dodgers uniform, is one of the featured players included in a video of Bruce Springsteen and the E Street Band highlighting TBS' postseason coverage.
With Springsteen's "Land of Hope and Dreams" as the musical backdrop, the videos include concert footage from the band's current "Wrecking Ball" tour and highlights from this year's MLB season. The videos will air on MLB Network, FOX and MLB.com and on in-stadium video boards leading up to and during the postseason.
Cahill is 1-0 with a 2.37 ERA in his last three road starts. The win came on July 30 against the Dodgers.