CHICAGO -- Before the season, the Oakland Athletics made a big, risky bet. They gambled on the proposition that former White Sox infielder Marcus Semien is a major league shortstop. After the A’s acquired him from the White Sox during the offseason and slotted him to fill the hole left by trading away Addison Russell and letting veteran Jed Lowrie leave via free agency, not many people believed he would stick. Asked for his take in spring training, one former GM said Semien’s arm wasn’t good enough for an every-day shortstop.

Early on, the critics were right. A third of the way into the season, Semien had committed a major league-worst 18 errors at shortstop, with minus-4 defensive runs saved. At the All-Star break, he had committed 28 errors, including 13 errant throws. His Ultimate Zone Rating at FanGraphs was an MLB-worst minus-14. As gambles go, Semien looked less like a big league shortstop and more like a good bet to become the first shortstop to commit 50 or more E6s in a season since Roy Smalley did it for the 1950 Cubs.

Semien was deeply frustrated, and didn’t know how to dig himself out of the hole he was in.

"I was letting one mistake lead to another. Things were not going well. I was in search of a routine to get me back on track, to help me know what to do to get better," Semien recalled of the ugly start to his season.

At that point, some organizations might have second-guessed themselves or the talent and started searching for alternatives. Instead, the A’s doubled down by reaching out to an old friend: Rangers manager and former A’s coach Ron Washington.

"It was on May 22, we were in Tampa Bay, coming from Houston, and I had just had a bad game," Semien remembers. "I was really down on myself. And that’s when I got the news that Ron Washington was joining the team."

Out of the game since his resignation from the Rangers job a year ago, Washington had gotten a phone call from Oakland GM Billy Beane, inviting him to rejoin the A’s as a special infield instructor.

"He called me and said, 'I have a kid here who has your name all over him. He could benefit from your drills and your knowledge of infield play,'" Washington said. "My response to him was, 'Well, Bill, if you want to make him a shortstop, I’m going to make him a shortstop.'"

"When I came in, there were a lot of people who told me, 'Wash, he can’t play shortstop,'" Washington recalled. "I looked at the video and I said to myself, 'There ain’t anything there that I can’t fix.'"

When Washington joined the team on the road on May 22, he immediately had a sit-down with Semien.

"I met him in the clubhouse," Semien remembers, "and he said, 'Before we work, let’s talk.' He wanted to see where I was at, and he wanted to introduce me to some things that would help me. And he saw what he thought could help me make more consistent throws."

"You can be the best teacher in the world, but if you can’t get your pupil to be on board, what you know don’t matter," Washington recalled. "He said, 'I wish you would have been here since Day 1,' and I said, 'I’m here now.'

And then they got to work.

"We just started with the basics," Washington said. "We had to make sure that he had a good bottom half -- his footwork -- to get that straightened out. And then we worked with how to use his hands. Then we began to graduate to more advanced stuff, slow rollers, going up the middle, having to spin. How to use the bag around second base to get leverage on his throws to first base. How to clear himself, how to protect himself, how to use his footwork different ways at second base on throws coming in that are not consistent."

Semien warmed to Washington’s intensive approach, noting: "Ron’s different, because the stuff he does I haven’t seen many other coaches do, with the different gloves that he’s got, or the close-up work that we do, and then once we go out there to throw, the way he sets up the drills are different from other infield coaches. Other coaches might run their drills a different way, hit a massive amount of fungoes. But he’s very close up, with specialized glove work, breaking down the mechanics of throwing the ball."

And what about the arm that so many doubted at the outset? Washington didn’t neglect that.

"What we did with his arm is help him understand his stride first," Washington said. "Each and every individual has a different stride. Once we figured that out, we talked about how to get a quicker arm. Then you start finding that consistency with his throws.

"He’s a tremendous student; he’s very smart," Washington adds. "He just didn’t know his position. It wasn’t his fault that he was making the mistakes that he was making -- he just didn’t know. Now he knows. You look at Marcus out there now, and he’s in charge -- he’s in charge of himself, and he’s in charge of the people around him."

All of which might point to Washington being a good coach: encouraging, engaged and full of faith in his players. And Semien’s second-half improvement in the field has been remarkable. His fielding percentage is up almost 50 points, to .973 from .925. Since June 1, Semien ranks in the MLB top 10 in defensive runs saved at shortstop with 5. Though his UZR is still last in the league, it’s almost three runs in the black since the break. And using Baseball Info Solutions data over that same stretch, his ratio of good fielding plays to defensive misplays & errors has gone from .034 to 0.63 -- not great (the MLB average is around 1.0), but up into Ian Desmond territory and headed in the right direction.

Through the power of the possible, Semien has gone from awful to asset. In short, he's looking like a shortstop.

"There was going to be some growing pains -- which there were -- but here recently, the last couple of months, it’s been a night-and-day difference," A’s skipper Bob Melvin observed. "He’s put in a lot of hard work at one o’clock in the afternoon with Ron Washington. For a guy who plays every day on top of that, it’s really a credit to how hard he works."

"He’s still not a finished product," Washington said. "There’s still a lot that we’ll address in spring training."

Washington will be there to help make it so; on Aug. 24, the A’s put him back in his old role as their third-base coach, replacing Mike Gallego.

Simply on the basis of his tools -- and particularly his arm -- Semien might have been written off as a shortstop by many observers at the outset. People looking at those MLB-worst 34 errors next to his name might still have written him off. But because he was ready to work at it and because Washington was available to work with him, Semien is a reminder that players are works in progress with the power to create their own upside.

As a result, that A’s bet that they have their shortstop? It might pay off yet.

Christina Kahrl writes about MLB for ESPN. You can follow her on Twitter.