SEATTLE -- Ron Washington has been in professional baseball since he signed with the Kansas City Royals in 1970. The only time he hasn't been in uniform and on the field was after he abruptly resigned as manager of the Texas Rangers last September for what he cited as family reasons. The Oakland Athletics hired him as an infield instructor in May and he returned to the field Monday when they made him their third-base coach in place of Mike Gallego.

"The main thing I'm looking forward to is being back on the field full time," Washington said before the Athletics played the Mariners. "I consider myself a difference-maker. What I was doing before [as an instructor], I felt like I was making a difference, but now I'll really be able to make a difference because I can be around to answer questions and be around to help these guys do certain things.

"I'm just happy to be back in the dugout."

Oakland manager Bob Melvin said there were a number of variables behind replacing Gallego, who had been the Athletics' third-base coach since 2009. The first he mentioned was the number of runners thrown out at home this year. The second was the awkwardness of having Gallego and Washington both coaching the infielders.

"I think we are at the top of the league in getting guys thrown out at home. And we have had a lot of one-run games," Melvin said. "And that's not a complete indictment on Mike. But I think, too -- and this is my fault -- it's been a little uncomfortable as far as the infield dynamic when you bring somebody else in to do some things when you have a guy who's been here a while, it's just a little uncomfortable."

Oakland had one of the best success rates scoring from second base on singles and from first base on doubles last season but has one of the worst rates now. They had two players thrown out at home Sunday, and Melvin said that might have brought the decision to a head though the team planned to make the move at the end of the season anyway.

Gallego told the San Francisco Chronicle he could see the writing on the wall in May when Oakland hired Washington as an infield instructor. Until Monday, Washington could not be in the dugout during games -- he usually watched from the press box -- because Oakland already had the maximum limit of coaches on the staff.

Prior to managing the Rangers, Washington was Oakland's third-base coach for a decade, so he knows what it's like to be under the magnifying glass when a runner gets thrown out at home.

"There is no perfection in the game of baseball," he said. "I don't expect to be a perfect third-base coach. But I know I'm a damn good third-base coach."

Washington managed the Rangers to their only two World Series appearances in team history. He said that should a managerial job opens up this winter he "definitely" would be interested. But for now, he said, he is focused solely on getting back in the third-base coaching box.

"He's a very energetic guy and very passionate about what he does," Melvin said. "Watching from the other side of the field, whether it was when he was coaching third or managing, I could see he brings a very energetic demeanor that rubs off on players. That's why he's been so successful."