OAKLAND -- It has outperformed a highly touted outfield group, and it might have even surpassed the performances of the rotation and bullpen, all things considered.
Indeed, the A's infield has evolved into the backbone of the 2013 team, a development no one would have expected in spring training.
When the A's assembled in Arizona to begin preparing for what has been another American League West championship season, the infield consisted of four question marks. There was a measure of doubt at every position.
The double-play combination was supposed to be Scott Sizemore at second and Japan's Hiroyuki Nakajima at shortstop. Sizemore played in two games before suffering a season-ending knee injury, and Nakajima had never played in the majors.
At the corners, Josh Donaldson showed promise at third last season, but his 2012 totals were nine home runs and a .241 batting average in 75 games. At first base, Brandon Moss hit .291 with 21 homers in 84 games, but there was uncertainty whether he could duplicate those numbers based on his journeyman résumé.
Eight months later, it all seems like so much wasted worry.
It's easy to point to the acquisition of Jed Lowrie from Houston in early February as the turning point, but manager Bob Melvin had the other uncertainties on the infield, too.
"We weren't really sure in spring training what position Lowrie was going to play," Melvin said. "It looked like Sizemore was going to be our everyday second baseman. We didn't know Eric Sogard was going to come on like he did. So we knew we might be flipping some pieces around as the season went along."
As it turned out, Lowrie almost immediately seized the shortstop position from the struggling and subsequently injured Nakajima. Sogard had a fabulous spring and forged a platoon with Sizemore, until Sizemore reinjured his anterior cruciate ligament -- in the same knee that sidelined him for all of 2012 -- in early April. Sogard was given an increased workload, which he handled with surprising aplomb.
Then came the stunning emergence of Donaldson, who exceeded everyone's expectations with an All-Star-caliber season at third base, batting .301 with 24 homers and 93 RBIs. Even general manager Billy Beane was knocked back on his heels.
"From the time he took over last August, he showed a lot of promise," Beane said. "But he hasn't stopped. He just kept getting better and better, and he's been an absolute grinder out there. To think how far this guy's come in a year, and to now hear chants of MVP, that's just so impressive."
Although Moss' batting average dropped to .256 this season, his 30 homers and 87 RBIs are more than last year's production. In addition, Moss has improved his defense despite playing left and right field when Josh Reddick and Yoenis Cespedes were dealing with injuries.
Also, the infield has had comparatively few aches and pains. Lowrie and Donaldson played in more than 150 games, Moss in 145, and Sogard in 130. None spent a day on the disabled list.
Good health is one reason Sogard thinks the A's infield was able to jell so quickly.
"Going into spring, it was kind of crazy," he said. "But once everyone finally settled in right around the start of the season, I feel like we clicked right away, and each day we continued to progress and develop a chemistry together. After that first month, it was like we were reading each other's minds and knew what we were going to do before it even happened."
Lowrie was a key. Beset by injuries throughout his career, no one knew if he would hold up.
"I've finally been lucky not to have had one of those freak injuries," said Lowrie, who batted .290 with 15 homers. "For years, I've always felt that was the only thing holding me back."
Added Beane, who made no secret in coveting Lowrie for years before finally acquiring him: "With Jed, there was never a question of whether he was a good player. It was just a matter of keeping him on the field."
While he has delivered the best offensive production the A's have had at short since Miguel Tejada, Lowrie felt his defense suffered at times because of 23 starts at second base, most in the first half.
"Defensively, it's been a bit of a trying year," he said. "I think I've made a lot of careless errors because it's hard to bounce around at those middle positions. Your footwork is different, arm angles are different, it's different on the double play."
The A's addressed that problem at the end of July with the acquisition of Alberto Callaspo from the Los Angeles Angels. He hadn't played second base in nearly three years and got off to a slow start, but he came on in September to provide a strong platoon with Sogard at second and allow Lowrie to play strictly shortstop.
Oakland also has had another positive development with the re-emergence of first baseman Daric Barton, who was called up when Moss was needed in the outfield. Barton is playing the best offensive baseball of his career, and he adds Gold Glove-quality defense at first.
"We have had some twists and turns over the course of the season," Melvin said. "But I think the flexibility that we had allowed us to do stuff kind of on the fly, whatever was best at that particular time during the season."
Moss had a simpler explanation.
"We didn't really have any revolving doors anywhere, particularly when we added Callaspo and Barton," Moss said. "We became a good group."
Said Beane: "We've had to mix and match here and there. But all in all, they've just done a great job."
Follow Carl Steward on Twitter at twitter.com/stewardsfolly.
A look at how the main components of the A's infield performed at the plate in 2013:
Infielder Avg. HR RBIs
1B Brandon Moss .256 30 87
2B Eric Sogard .266 2 35
SS Jed Lowrie .290 15 75
3B Josh Donaldson .301 24 93
Brad White/Getty Images
Corner infielders Josh Donaldson (20) and Brandon Moss (37) have provided much power for the A's.
ALDS: A's vs. tigers
Friday: At Oakland, 6:37 p.m. TBS
Saturday: At Oak., 6:07 p.m., TBS
Monday: At Detroit, time TBA
Oct. 8*: Oakland at Detroit, TBA
Oct. 10*: Detroit at Oakland, TBA
*-- if necessary