A sinkerballer by trade, the 21-year-old rookie allowed only eight home runs in 238 2/3 Minor League innings over parts of three seasons.
After allowing solo shots to Hank Blalock and Michael Young in Thursday's 6-4 loss to the Rangers, Cahill has now surrendered 25 homers in 126 1/3 innings this season -- second-most in the American League.
"It's different, definitely," Cahill said. "In the Minor Leagues, I really didn't give up that many. I've been getting hurt with a lot of them. ... It's frustrating. You want to throw zeroes up there."
"He's got a good arm," Young said. "He has been tough on us before, but today we were a little more patient and he got a couple of balls up."
Cahill gave up five earned runs on eight hits in six innings. He's allowed at least one home run each of his past nine starts and is now 1-6 with an 8.19 ERA in 40 2/3 innings over his past eight outings.
"He was better today," manager Bob Geren said. "When you're around the plate, [home runs will] happen once in a while. It was an improved outing for him.
"His changeup will keep improving. As soon as he can throw his fastball to both sides of the plate, that home run number will go down."
Fellow rookie Tommy Hunter, 23, didn't have many problems with the A's lineup. The Rangers starter held Oakland to three runs (two earned) on three hits in seven innings. Two of those runs came across in the first.
"I thought we got a couple good swings on him early," Geren said. "We had those early chances, but after that he started settling in pretty well."
Hunter improves to 4-2 with the win. He has a 2.63 ERA through 48 innings this season.
The A's looked like they had something going with a two-out rally in the ninth.
Tommy Everidge singled, then Scott Hairston, pinch-hitting for Ryan Sweeney, brought him home with a double down the left-field line.
Following a pinch-hit walk by Kurt Suzuki, Rangers closer C.J. Wilson got Mark Ellis to fly to left to end the game.
"It was kind of off the end of the bat, just not quite off the barrel," Geren said of the ball Ellis put in play. "It was just a couple inches away from us jumping up and down and celebrating."
Young, David Murphy and Andruw Jones had two hits apiece and each scored a run. Young pushed his hitting streak to 13 games, the longest of the season by a Ranger. Marlon Byrd extended his hit streak to eight games by going 1-for-3.
Everidge went 1-for-4. He's started and reached base in each of his 10 games since being called up from Sacramento. The 26-year-old is batting .263 through 38 at-bats.
Ellis had his season-high 10-game hitting streak snapped.
Adam Loberstein is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.