Haren allowed two runs on seven hits over five innings as the Class A Advanced 66ers topped the Lake Elsinore Storm, 5-4, on Monday. He struck out two while not allowing a walk and threw 44 of his 65 pitches for strikes.
After struggling through the third inning and giving up RBI singles to Rico Noel and Justin Miller, Haren settled down over his last two innings, facing one over the minimum.
"I felt different tonight," Haren said. "I was a little bit out of sorts to start. The last inning was my best inning I thought. I felt good, my fastball especially felt good there at the end. That's the most important pitch for me. Being able to throw everything off my fastball, I just haven't had anything on my fastball.
"It was good work and I'm glad I did it. We talked about doing a simulated game, but I think it was better to get lefties and righties up there."
Haren was placed on the disabled list on July 5 with lower-back stiffness, an ailment that has plagued him all season. The Pepperdine product is 6-8 with a 4.86 ERA in 17 starts.
"It wasn't necessarily pain, it was inflammation, stiffness," Haren said. "Every time we'd get a bead on it, I'd get back on the mound and it would flare up on me. I couldn't get a hold on it and I needed to take a little bit of a break and do some exercise and take a few medications.
"Even since the spring, I haven't been the same. Even games like in Seattle, where I threw a complete-game shutout, I wasn't feeling like I was last year. I still was a little bit stiff. The last time in Cleveland put me over the top, I wasn't helping the team."
Haren is expected to rejoin the Angels rotation this weekend in a series against the division-rival Texas Rangers.
"I'll be good to go," the 31-year-old right-hander said. "I wanted to make sure everything went fine today and they wanted to make sure I came out of everything good. We'll see how I feel in the morning."
In 10 Major League seasons, Haren is 113-92 with a 3.66 ERA. The three-time All-Star has made 254 starts since 2005 and had never been on the disabled list in his career, a point of pride for the hurler.
"I kind of had to swallow my pride, having the consecutive starts streak and wanting to go out there and help the team," Haren said. "I think the competitor in any pitcher feels that, at any percentage, you can go out there and get people out. I felt like going into the All-Star break was the best time to take two weeks off and get better."
For a veteran who had not seen the Minor Leagues since playing for Memphis in 2004, Haren made sure to stick to the tradition of giving the younger guys a taste of the bigs.
"It's been fun hanging out in there. I know a few of them from spring. It seems like a close-knit group of guys. We spread it out, instead of getting one big one [meal], we did a couple of smaller ones. I think the guys appreciated it."
Manuel Flores (1-1) picked up the win in relief, allowing one hit over two shutout innings. Daniel Tillman pitched a perfect ninth for his third save.
Rolando Gomez hit a two-run homer in the eighth to put the 66ers ahead and C.J. Cron, the Angels' No. 2 prospect, drove in his 76th run of the season.