When Ron Washington began working with Marcus Semien in 2015, the A’s shortstop lacked some of the basics at the position.

“I wasn’t even holding my glove correctly,” Semien said. “Wash had to tell me to spread my hand to give the glove the widest surface, and then give the glove a push through the ball to eliminate any funky hops.”

The pairing of Washington, the longtime A’s coach and the winningest manager in Rangers’ history, and Semien, an everyday big-league player relearning defensive fundamentals during a season, was different, but it worked and then some. Semien went from having the worst season in the field in Oakland history in 2015 to being a Gold Glove finalist last season.

Semien knows the debt he owes, and Jan. 9, he will honor Washington at the fifth annual Coaching Corps Game Changer awards.

“It was pretty easy to pick Wash,” Semien said. “Wash is the guy, it was a no-brainer. The time I spent with him on the field working for a year and a half, we put in more hours than I have with any other coach. I was lucky the team hired him.”

With different personalities, things might have gone south quickly, but Washington was willing to join the A’s as the infield coach after eight seasons running the show in Texas. Washington, who resigned as the Rangers’ manager after the 2014 season, had been an Oakland coach from 1996-2006, and he was receptive when called by Billy Beane, A’s vice president of baseball operations who was then the general manager.

“Billy could have let me sit at home, but he called me and said, ‘What are you doing? I have a kid here who needs you and I know you need this kid. How soon can you get here?’” Washington said of Beane, his former Twins teammate. “But it was Billy and David Forst (then assistant GM) believing in Marcus. They knew what I could bring to the table and the process started.

“I have to give Bob Melvin credit, too. He let me do my thing and didn’t look over my shoulder. He believed in me. Here’s a manager who’s just finished managing — and the team’s manager trusted me to come into his house and do what I had to do.”

Semien, meantime, took no offense at the notion that he needed a fielding revamp. He was eager for instruction.

“This kid was tremendous,” Washington said. “I always say, I’m just a provider and if your pupil can’t apply what you’re trying to get them to do, you’re actually worthless. Marcus doesn’t make me worthless. He’s intense, he has tremendous character, he’s a winner and he wants it bad.”

Semien, who is from El Cerrito and played at Cal, was acquired from the White Sox in the Jeff Samardzija deal, and he went from being an occasional utility player in Chicago to a full-time big-league shortstop. He made 16 errors in the first six weeks of the 2015 season.

“He was at a level of confusion,” said Washington. “Marcus was playing shortstop and he had no direction; that’s how I saw it. I just didn’t see the knowledge of how to play the position, the little intricacies. That was missing.”

Washington, 66, said he told Semien that if he was willing to work hard, they’d turn him into “exactly what you want a fielder to be: efficient and consistent. From the day I met him, he was on board; he never backed off,” Washington said.

Most important, according to Washington, was ensuring Semien was always in proper position to field the ball: that he was in the right spot before the pitch, that he reached the ball quickly with his hands at the correct angle, and that he took the correct stride to make a strong and accurate throw. Once those things were established, Semien would be prepared to fix his own mistakes — he’d understand how he’d made a particular error or why his stride resulted in a poor throw.

Semien finished that first season with an Oakland record 35 errors, but the following year, he made just 21 and in 2018, he made 20. He was credited with a career-best nine defensive runs saved, and FanGraphs calculated his defensive runs above average at 15.6, ahead of Gold Glove teammates Matt Chapman and Matt Olson.

“Sometimes in this game, when you have to start all over again, people think you’re never going to make it — but that’s not the case,” Washington said. “Marcus had to start from scratch and learn what he had to do, understand the thought process behind it, and that first year it was setting the foundation. The next year, he made tremendous strides and this last year, he took it to another level. I think he can continue to take it higher and higher.”

Semien, 28, said that Washington did more than just prepare him physically.

“The confidence is everything, I think,” he said. “Mechanics are one thing, but if you don’t have confidence, what’s the point? Wash helped me with that mental game, and that’s what a good coach does.”

Other Bay Area athletes — and the coaches they will honor — at the Game Changer ceremonies include Warriors’ guard Klay Thompson (and Santa Margarita High coach Jerry DeBusk), Giants infielder Pablo Sandoval (manager Bruce Bochy), 49ers’ receiver Marquise Goodwin (high school coach Richard McCroan), Cal basketball player Kristine Anigwe ( coach Lindsay Gottlieb), and retired Raiders’ defensive back Charles Woodson ( Michigan defensive backs coach Vance Bedford).

Semien is a little nervous about presenting Washington with his award, “but I want to make sure that everyone knows what he’s done for me,” he said.

He suspects he might get a little emotional when Washington takes the stage, and he also thinks the famously profane Washington will give NBC Sports Bay Area’s censor button a workout. “They’ll probably have to do some editing for the broadcast,” Semien said with a laugh.

Washington has been honored by an A’s defender before; third baseman Eric Chavez gave Washington one of his Gold Glove awards. For Washington, though, the real reward comes during the work itself.

“It was definitely school, and it was a class I enjoyed,” Washington said. “Undoubtedly, Marcus enjoyed it too, because the results are there. When we were done, I told him, ‘I’m going to cut the umbilical cord, because you’re ready to go.’”

Susan Slusser is a San Francisco Chronicle staff writer. Email: sslusser@sfchronicle.com Twitter: @susanslusser