"When A's officials sift through the wreckage of a disappointing 2011 season, inconsistent pitching and hot-and-cold hitting will stand out.

They can take heart, however, in an infield that shows promise for the future. And the cast delivering that optimism could not have been foreseen back in April.

Shortstop Cliff Pennington is the only holdover from the A's opening night starting infield.

Fleet-footed rookie Jemile Weeks has replaced veteran Mark Ellis at second base. Scott Sizemore has adjusted well to third base in place of Kevin Kouzmanoff, and Brandon Allen has shown enough since arriving in a July 31 trade from Arizona to suggest he could be the answer at first.

"I think the infield has some ways to go, but it's a good start," A's general manager Billy Beane said. "It's a young infield, and it has the ability to be very good."

Certainly, Beane and his staff will want to see tighter defense.

Weeks leads American League second basemen in errors despite not getting called up until June 7. Pennington's 21 errors are second-most among shortstops, and Sizemore has committed 13 since being recalled from Triple-A on June 6.

"We're going to work on our defense," said A's manager Bob Melvin, who talks hypothetically about 2012 because he's still the "interim" skipper. "If this group stays together going into next spring -- all of us -- it is something to build on because they have gotten better."

Pennington's offensive production in the second half has grabbed notice. He's hitting .309 with 35 RBIs since the All-Star break, and his season-long .351 average with runners in scoring position ranks fifth in the A.L."