From Chronicle Staff Writer Susan Slusser at the Coliseum

Jason Hammel will leave for the birth of his second child after Thursday’s game and will miss his next start, The Chronicle has learned, so left-hander Drew Pomeranz will start on Saturday against the Phillies. Hammel will rejoin the team after the weekend. He presumably would slot back in the following Thursday at Texas, with the rest of the rotation set pretty much as the A’s would like the rest of the way.

Hammel has bounced back strong after a rough initial month with Oakland; he hasn’t allowed more than three runs in any of his past five starts. Pomeranz pitched very well in his one start in the second half, going 5 1/3 innings and allowing three hits and one run, not earned, at Houston last month.

Pomeranz, who has been in the bullpen since, hasn’t worked in two weeks, but he did throw to hitters today and he said it went well. “Getting a little refresh,” he said.

Jon Lester will start Friday against Philadelphia, keeping him on normal rest and also keeping him in line to start the wild-card game Sept. 30, which he has been slated for for weeks.

Stephen Vogt was one of the hitters to face Pomeranz today, and he’s taking batting practice right now, but he’s not expected to be available today and might not be back tomorrow because of a left ankle sprain. He could be used as a pinch hitter as soon as Thursday, though. He still will not be able to catch, nor will he again this season with that right foot problem, but the hope is that Vogt will be able to play first base and in the outfield by this weekend.

Outfielder Craig Gentry remains out with a concussion and he’s feeling extra bad now because he has a sinus condition on top of it. That sounds like an awful combination.

Catcher John Jaso is unlikely to play again this season because of a concussion. He is not yet doing baseball activity and there is no indication he will be scheduled for any with just two weeks left.

Catcher Geovany Soto, though, is available today, feeling “good to go,” he said, after back spasms last weekend.

Here’s the lineup vs. the Rangers and right-hander Nick Tepesch: Crisp CF, Fuld LF, Donaldson 3B, Dunn DH, Moss 1B, Lowrie SS, Reddick RF, Norris C, Sogard 2B. It’s Scott Kazmir on the mound for Oakland.

Shortstop Jed Lowrie is the A’s nominee for the Roberto Clemente Award, given each year to one major-league for on and off field contributions. Lowrie and his wife, Milessa, started the Jedi Warriors program to host veterans at games.

If you missed it in today’s Chronicle, Billy Beane, opponents and scouts weigh in on the A’s postseason chances.