Competing for the No. 3 spot in the San Diego rotation, Ross struck out three in three innings and walked two. He has thrown five hitless innings in two starts.
Milwaukee didn't get a hit until Elian Herrera tripled leading off the sixth on a drive that center fielder Rico Noel lost in the sun. Scooter Gennett followed two batters later with a two-run homer, just his second hit in 15 spring training at-bats.
Noel hit an inside-the-park home run in the fourth.
Ryan Braun went 0 for 2 with a walk after getting hits in seven of his first eight spring training at-bats.
Milwaukee starter Matt Garza gave up three runs - two earned - and six hits in three innings, giving up a leadoff homer to Alex Dickerson in San Diego. He had allowed four runs, four hits and two walks in one inning and Colorado last Sunday in his first start.
''I was more in control. Not less energy but more controlled energy, Garza said. ''The first time out is a lot more anxiety, a lot of excitement. I felt great today. Everything was in line and everything was under control, and I was able to throw strikes.''
Padres: Ross retired eight of the 10 Brewers he faces over three innings.
''Another solid outing and step in the right direction,'' he said. ''I had a chance to extend my pitch count (28 of 41 pitches for strikes), get up and down three times and feel really good. I missed a couple of pitches to Braun, but you can afford to make mistakes with him. I was definitely careful there.''
Brewers: Garza was in trouble right from the start. He allowed six hits and two earned runs in the first two innings before closing with a strong third inning, striking out Carlos Quentin and Xavier Nady.
Milwaukee's defense hurt Garza, too. Juan Francisco missed a chopper at third base and Elian Herrera misplayed a line drive to center into a run in the first, and a poor throw to the plate led to another in the second.
''It's always a good test, because it's adversity, and you just have to focus on keep making your pitches and don't worry about things you can't control,'' Garza said. ''Once I let it go, then it's out of my hands, figuratively and literally.
''Keep making pitches and these guys will pick you up more than they let you down,'' he said.
ONE, TWO, THREE DIVES ... YOU'RE OUT!
It was an interesting day in sunny center field for Herrera, the Milwaukee utility man.
In the first inning, he made a diving lunge for Nady's flyball and had it bounce off his glove as a run scored. In the fourth, he made a long run but dived and missed what became an inside-the-park homer for Noel.
''It was a tough play and I think I have a chance to get it,'' said Herrera, who landed on his chest, chin and nose and stayed down as Noel ran. ''It was a ball in the gap and even if I don't try that, the ball is going to so in the gap no matter what. I tried.''
The third time, Herrera made a diving grab of Quentin's sinking liner to end the inning. Then he was repaid in the sixth when Noel lost his line drive in the sun and he was credited with a triple.
''At least I'm hitting,'' he said with a weak smile.
The Padres claimed outfielder Alex Castellanos off waivers from the Texas Rangers.
Castellanos appeared in 27 games with the Los Angeles Dodgers over the past two seasons, hitting a combined .171 (7 for 41) with a double, triple and two home runs. He batted .257 with 19 home runs, 61 RBIs and 19 stolen bases with Triple-A Albuquerque Dukes last year.
Castellanos was 3 for 9 this spring before being designated for assignment by the Rangers on Thursday.
To make room on the 40-man roster, the Padres placed left-hander Cory Luebke on the 60-day disabled list. Luebke underwent Tommy John surgery on his left elbow on Feb. 18.
Brewers third baseman Aramis Ramirez will make his debut on Saturday against the Kansas City Royals. Ramirez, who underwent surgery in January to remove a non-cancerous polyp from his colon, ran the bases full speed on Friday morning, passing the final test from manager Ron Roenicke.
Ramirez said he feels like he has plenty of time to ease into things and still get ready for the Mach 31 season opener.
''I'm going to have to take it easy earlier,'' he said. ''I'm going to have to play at least three, four in a row (heading into the season). I can't do that right now.
''We've still got, what, 20-plus games counting the two exhibition games at home? I should be good,'' he added.