By Morris Phillips

After another win over the Astros and the sweep of the weekend series, you have to be wondering: why are the A’s so good?

A lot of reasons for sure, but how about this: the A’s have had incredible success plugging guys—often complete neophytes—into roles and having them fit near perfectly. The stars of Oakland’s 4-1 win on Sunday provides examples of the A’s run of success of getting production from unlikely sources.

Starting pitcher Jesse Chavez picked up the win, going six innings without his best stuff. But the journeyman reliever turned starter—even at the advanced age of 30—is evolving. Chavez has added a cutter and changeup to repertoire which was apparent to the A’s when they acquired him in August 2012 on the heels of Bartolo Colon’s 50-game suspension for using performance-enhancing drugs. The A’s felt that Chavez could make the transition from reliever to starter, based on his major-league quality arm and variety of pitches, skills that hadn’t translated to major-league success in his parts of six seasons of big league experience.

So what did the A’s see from the reliever who had a 5.72 ERA in 152 appearances when they acquired him in 2012? For one, a guy who was hungry, motivated enough to add pitches to his repertoire and already in possession of a fastball consistently above 90mph. With the addition of the cutter and the changeup, Chavez had enough of arsenal to start, so the A’s placed him in that role at Sacramento. Now, nearly two seasons since his acquisition, Chavez in the A’s rotation in place of injured starters Jarrod Parker and A.J. Griffin.

So what does he do with the opportunity as a caretaker until bigger names and better arms regain health? Chavez allows one earned run in each of his first four starts to become the first A’s pitcher in franchise history to go at least six innings in each of his four starts and allow one earned run or less. And Chavez didn’t even have his best stuff on Sunday in lowering his ERA to 1.38, the best on the staff.

“The only thing I had pretty much working today was my changeup,” Chavez said. “That was a good pitch that I needed.”

“That’s really the mark of a good pitcher, when you don’t have your best stuff,” manager Bob Melvin said of Chavez. “He’s been focused and ready for that opportunity and continues to run with it.”

Luke Gregerson was part of some pretty good bullpens in San Diego where he made 373 relief appearances in five seasons. But the sinker ball specialist has never been a full-time closer, compiling 132 holds and just 16 saves as the Padres’ setup man. But when Jim Johnson struggled to start the season, Melvin tabbed Gregerson to be one of his closers by committee.

Now—three saves later—Gregerson looks like they guy even if he doesn’t ultimately assume the role. When Johnson faltered, it could have turned into a major problem for the A’s, but they’ve turned the dilemma into a plus by reaching for a quality arm in their deep and talented bullpen. The fact that the former Padre is well-compensated for his services–making better than $5 million this season in the final year of his contract—takes much of the pressure of Melvin, who can use the reliever in either role. Either way, Gregerson’s established and doesn’t have to worry that his value might diminish if he isn’t overwhelmingly successful in the new role.

Gregerson needed just nine pitches to record three outs in the ninth, lowering his ERA to 1.69.

Sunday’s offensive hero was Josh Donaldson who smashed a two-run homer in the first and later added a pair of doubles. The former catcher who was acquired from the Cubs in 2008 in the Rich Harden trade made his first major league appearances in 2010 as a catcher entrusted to spell Kurt Suzuki. But that role didn’t allow Donaldson to stick with Oakland, and he wasn’t again seen on the big league level until 2012 when the A’s needed a stop gap to replace injured Scott Sizemore at third base.

Needless to say, Donaldson has established himself at third base, working hard on his defense while smashing 24 home runs and knocking in 93 runs in his breakout 2013. But what’s really remarkable about Donaldson is that he has established himself as a middle-of-the-order presence by cutting down on his strikeouts, and learning how to consistently hit deep in pitch counts.

Where would the A’s be without the slugger from Alabama? In a much darker place for sure. Seth Smith never established himself as an everyday player and was traded in the offseason. Yoenis Cepedes has played spectacularly at points, but his inconsistent bat explains why doesn’t regularly hit fourth or fifth. And Josh Reddick, Brandon Moss aren’t nearly high enough for average hitters to qualify for a role in the middle of the order either.

But Donaldson has taken to the role perfectly, hitting for a high average and providing pop. This from a guy who didn’t get a look at the big-league level in 2011 and changed positions for the benefit of the A’s more so than for himself.   Now Donaldson is giving the A’s exactly what they need when the cost of acquiring a middle-of-the-lineup presence is prohibitive.

And Donaldson’s salary? In 2014, the former catcher is big bargain, earning just $500,000.

On Monday, the A’s take on the Rangers at the Coliseum with Texas ace Yu Darvish facing Dan Straily.