ANAHEIM -- For the three highly touted rookies in the A's starting rotation, the four-game series that opened on Thursday at Angel Stadium will double as something of a progress report.
Trevor Cahill, a 21-year-old right-hander, Brett Anderson, a 21-year-old lefty, and Vin Mazzaro, a 22-year-old righty, each have a start against the host Halos, and how they perform against the class of the American League West should provide something of a measuring stick.
How far have they come? Are Cahill and Anderson, who have been with the team all season, appreciably better than they were in April? Has Mazzaro, who lit it up in his first two starts after being recalled from Triple-A Sacramento but struggled in the aftermath of his splashy debut, righted himself?
The Angels might provide some answers. Oakland manager Bob Geren provided some of his own before the opener of the series.
Geren said all three of them have improved, although he hedged a touch when discussing Mazzaro, who won his first two starts without allowing a run but lost his next eight decisions and will take a 4-9 record with a 5.32 ERA into his Saturday start.
"That's a little harder measuring stick because his first two starts were so good," Geren said while chatting with the press in the dugout as his players stretched for batting practice in 100-plus heat. "He's made improvements in the last month, but it's hard to improve on his first two starts; he was so dominating."
Regarding Cahill, who was called for the opener on Thursday, and Anderson, who'll get the ball on Sunday, Geren was more specific.
"Trevor's gotten a lot more consistent with his arm slot, and his slider's really improved," said the skipper. "Brett's been pretty darned good all year, but he's definitely gotten better at getting left-handed hitters."
That said, Geren didn't see the Angels set as any more significant than some of the other series in which the youngsters have worked recently.
"They've also pitched against Detroit, the Yankees, Boston; they get tested all the time," he said. "Playing against the best team in the division, it's just another test."
Anderson, who is 7-6 with a 4.35 ERA, posted a 1.87 ERA in five starts in July but has a 4.41 ERA in five starts in August. Mazzaro is 2-4 with a 7.45 ERA in eight starts since the All-Star break.
"I do think, collectively, they've gotten better," Geren said. "They're better from sheer experience."
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.