OAKLAND, Calif. -- Bob Melvin stares intently and watches Josh Donaldson take batting practice. The other Oakland A's players joke around as they wait their turn in the cage. A's owner Lew Wolff is there, and chats up Ken Korach, the team's radio play-by-play broadcaster. But Bob Melvin stands quietly behind a net, halfway up the third base line, and stares. The A's manager was nervous that Donaldson and teammate Yoenis Cespedes would alter their swings for the Home Run Derby and return from the All-Star break with bad mechanics or, worse, an injury. He's relieved with what he's seen from Donaldson and Cespedes in the week since.

There was no nervousness, though, when Melvin watched six A's take center stage for the American League in the All-Star Game -- Donaldson, Cespedes, Brandon Moss, Derek Norris, Scott Kazmir and Sean Doolittle. Melvin felt only pride. "You'd normally have a phenom coming up and making his mark and going to an All-Star Game," he said. "To be able to see all those guys out there, so many A's, was rewarding and a testament to how hard these guys have worked. It was a great story."

But how exactly did this roster become such a juggernaut?

Donaldson was drafted by the Chicago Cubs in 2007 out of Auburn University and traded to the A's the next year when the Cubs acquired Rich Harden. He toiled in the A's minor league system for three-and-a-half seasons. He was a catcher who could also play third base. He hit for average and took his walks, but his power numbers dropped when he reached Sacramento, where the A's Triple-A franchise plays. His big break came in 2012 when the A's expected third baseman, Scott Sizemore, tore the ACL in his left knee on the first day of spring training. That day, Donaldson asked Melvin if should move to third. Melvin said yes and the next day told Donaldson to put away his catcher's gear. He then played his way onto the Opening Day roster.

But Donaldson struggled to hit and found himself back in Sacramento, replaced by Brandon Inge, who'd been released by the Detroit Tigers. Donaldson reclaimed third base in mid-August and hasn't looked back since. He hit .301/.384/.499 last season and played spectacular defense at third. He was the third-most valuable position player in the league, according to FanGraphs and finished fourth in American League MVP voting. This season, he was the starting third baseman for the American League in the All-Star Game.

Brandon Moss traveled a similar, non-traditional path to All-Star status. The Red Sox drafted Moss out of high school in 2002 but he didn't see the majors for the first time until 2007. He played everywhere in the field while in the Red Sox's farm system but saw time only in the outfield after his call up to the majors. Moss was hitting .295/.337/.462 when the Red Sox shipped him to the Pittsburgh Pirates in 2008 as part of the Manny Ramirez-Jason Bay trade. The Pirates asked Moss to change his swing, to try to take the ball the other way, despite his success as a pull hitter. He struggled through the 2009 season and found himself back in the minors, first with the Pirates in 2010 and then with the Phillies in 2011. At age 28, his career looked bleak.

Then the A's signed him to a minor-league contract before the 2012 season. Moss looked at the logjam in the A's outfield -- Cespedes, Coco Crisp, Josh Reddick, Johnny Gomes and Seth Smith -- and knew the only way he'd make it to Oakland was by playing first base. So he asked his Triple-A manager Steve Scarsone if he could get time at first. Scarsone said yes and on June 6, 2012, Moss made his A's debut with a start at first base.

Moss's slash in 322 games for the A's over the last three seasons is .268/.345/.541 with 73 home runs. He ranks in the top 20 of the most valuable position players in the American League, according to FanGraphs. And, for Bob Melvin, he's been invaluable. When Josh Reddick suffered a knee injury in early June, Moss was back in right field, where he'd played sparingly since 2012. "I'm an offense guy," Moss said. "I'll play wherever they need me so I can stay in the lineup," adding that players need to be flexible to succeed. "Even Mike Trout has changed positions," Moss noted.

It's not just the All-Stars. Every player who has put on an A's uniform this season has moved around the field, the lineup, the rotation or the bullpen. In their first 100 games, the A's used 75 different lineups and 81 different batting orders (not including pitchers). By contrast, in their first 98 games, the Detroit Tigers used only 54 different lineups and 70 different batter orders (sans pitchers). For the Baltimore Orioles, those numbers are 55 and 59 in 100 games.

Perhaps the A's flexibility mantra is no more evident than in Stephen Vogt. Oakland acquired the minor-league catcher from the Tampa Bay Rays at the start of the 2013 season for cash. Vogt had bounced around the Rays' farm system for more than five years and when he finally got his chance in the majors, he went hitless in 25 at bats. When A's catcher John Jaso suffered a season-ending concussion, Vogt got the call to Oakland, where he hit .252/.295/.400 in 47 games.

With Jaso healthy, Vogt started this season back in Sacramento where he hit .364/.412/.602 -- eye-popping numbers even in the offensively-charged Pacific Coast League. When Reddick went down and Melvin asked Moss to take some time in right field, the A's needed someone to play first base. And when Moss was back at first, someone to play in right field. Maybe left field, too. And a few games behind the plate. That someone is Vogt.

Since his June 1 call-up, Vogt has played more than 105 innings in right field, more than 65 at first base and more than 85 at catcher. He played one game in left. He's had at least three at bats in every spot in the batting order, except for third and fourth. Oh, and he's hitting .355/.386/.516 in 132 plate appearances.

Vogt is non-plussed about what his manager has asked him to do. "I talked with Bob and the other coaches when I got to Oakland, and they asked me my comfort level in the outfield," Vogt told me recently. "I said 'I'm comfortable, it's just been a while.' So they eased me into it." I asked Vogt how far in advance he knows what position he'll be playing on any given day. "Around one o'clock, when I get to the ballpark." Is it difficult to get ready with so little time to physically and mentally prepare? "Not really," said Vogt. "I just put in my work for whatever position I'll play that day. It's all about me being honest with Melvin and the coaches."

Of course, a lot of the credit for the way this A's team has gelled should go to the way the manager has handled all these moving parts. The players certainly appreciate it. "Bob gives us constant feedback," said Vogt. "He's always asking how we're doing. He's always giving us a sense of where he is with us. I've never played for a manager that gives that much feedback. He talks to Billy [Beane] and the front office. It's just an open communication with everyone."

Echoed Jaso, "If someone is hot and playing really well, some managers will ride that player until he gets cold. BoMel will keep the player doing what he's doing. I only play against right-handed pitchers. If I was hot, he wouldn't put me in against lefties. It keeps my hot streaks going longer."

For his part, Melvin isn't interested in talking about himself as a reason for the A's success. Nor does he want to talk about how the A's can get to the next level this season, past a division title and deep into the postseason. "We have to get there first. Our whole mindset is about today's game. If you get farther out than that, it's a distraction," he said. "One of the strengths of this team is being able to focus on today and giving our complete effort. We're not thinking a week down the road, let alone October at this point."