SAN DIEGO -- Luis Perdomo's frustrating season took another frustrating turn on Friday night.
The Padres right-hander was removed in the third inning of a 6-2 loss to the D-backs, and the news only got worse from there. Afterward, Perdomo informed the club of soreness in his throwing shoulder. He's probably bound for the disabled list, though the extent of the injury remains unclear.
"My guess is it's highly unlikely he makes his next start with the way he's feeling right now," manager Andy Green said. "We'll make a determination in the next 24 hours and go from there."
This particular injury is nothing new for Perdomo, who has twice missed time with shoulder soreness in his career. On both occasions he was back shortly after the minimum disabled-list stint. The Padres are optimistic for more of the same this time around, but it's too early to tell.

Friday's outing was a particularly discouraging one for Perdomo, given that he was coming off his best performance of the season in Philadelphia last weekend. Too often, it seems, Perdomo has hinted at progress, only to take a step backward in his next start.
Center fielder Manuel Margot put Perdomo on top, 1-0, with a moonshot into the second level of the Western Metal Supply Building in the bottom of the second. It extended Margot's hitting streak to a career-high eight games.

That lead didn't last long. Perdomo's third inning unraveled quickly. He allowed four doubles, two singles and two walks before his exit. He was charged with six runs over 2 1/3 frames, and his strikes were entirely too hittable once again.
"It's a disappointing third inning, and disappointing news after the game, too," Green said.
Now, there's a vacancy in the Padres rotation, and there are no shortage of options to fill it. Jordan Lyles is nearing his return from elbow inflammation, but he's struggled in two rehab outings for Triple-A El Paso.
Robbie Erlin was excellent in long relief on Friday night. After 3 2/3 scoreless frames, Erlin lowered his ERA to 2.05 as a reliever. But in two starts, he's surrendered 11 earned runs in seven innings.
Perhaps the most intriguing candidate is right-hander Brett Kennedy, an 11th-rounder from the 2015 Draft who is not on the 40-man roster. He pitched six innings of two-run ball on Friday night and owns a 2.56 ERA in 15 starts for El Paso.
After the game, Green hinted that Kennedy might be an option. Of course, Tuesday's non-waiver Trade Deadline could throw another wrench into his rotation plans.
"We obviously have Jordan down there rehabbing, and we have other guys that, at some point in time, we've got to look at because they're throwing the ball well in Triple-A," Green said. "We'll wait and see."
ON A ROLL
The hottest hitter on the Padres these days? Take your pick: It's Margot or Austin Hedges.
Given the way they started the season -- and their presumed importance in the Padres' future -- that's a very noteworthy development. Margot homered Friday and went 2-for-4. Hedges went deep for the second time in as many games, a solo shot in the eighth.

"Those two guys have been really, really good," Green said.
Margot's bounceback was incremental. He underwent a complete overhaul in his swing after he bottomed out in mid-May. Since the start of June, Margot is hitting .308. His on-base percentage is back to league average for the season.
Hedges, meanwhile, has been red-hot since he returned from an elbow injury in mid-June. He's hitting .327 with four homers in July.
Both Margot and Hedges are outstanding defenders, but their long-term offensive value remains a question mark. In that regard, the past month feels like a step in the right direction.
STOCK UP
Perdomo's early exit meant the San Diego bullpen needed to pick up the slack. Erlin did his part, and rookie Robert Stock followed with a second straight impressive showing.
The flame-throwing right-hander pitched two scoreless innings, allowing only one hit on Friday night. In the top of the seventh, he worked around a leadoff error and retired the heart of the D-backs' lineup in order.
Stock -- who touched 99 mph and owns the 21 fastest pitches thrown by a Padres pitcher this season -- now has five scoreless innings since his four-run blowup a week ago in Philadelphia.
HE SAID IT
"I'm going to put in the same sort of work, regardless of how I'm playing. Whether I'm playing well or not playing well, it's the same." -- Margot
UP NEXT
Tyson Ross' name has come up in all sorts of trade chatter over the past month. He's slated to make his final start before Tuesday's non-waiver Trade Deadline on Saturday at 5:40 p.m. PT. Arizona counters with left-hander Patrick Corbin. Ross appears to have put his early July struggles behind him. He allowed 15 runs in his first two starts of the month, but he's allowed four over his last two.