Washington’s Ryan Zimmerman, shown working out in spring training, has been making a successful transition from third to first base this season for the Nationals. (Jonathan Newton/The Washington Post)

Three Washington Nationals have started every game so far: Ian Desmond, Bryce Harper and Ryan Zimmerman. Harper has drawn attention like he has drawn walks: daily and more than anyone in the majors. Desmond could not evade notice early on because as balls slipped away at shortstop in April, he stumbled into the spotlight, too.

All the while, Zimmerman stood at first base, unnoticed relative to the other two and to his teammates. He is again a quiet cornerstone, albeit at a different corner, absorbing the lessons of a new position so efficiently it is easy to forget he played third base a year ago.

Though he has yet to assume his typical rhythm at the plate, Zimmerman has played steadily at first. By the standards of an eye test or defensive metrics, he has become one of the league’s best at the position. The process has taken all of 31/2 months.

For first basemen, whose job predominantly is to finish plays started by others, high scores on the eye test are earned by those who catch the eye the least. Good first basemen grab everything, fielding ground balls hit their way and scooping low throws to prevent outs from becoming more conspicuous errors. Zimmerman has done all those things, particularly the latter, like a more experienced first baseman.

“I’m not gonna say that he hasn’t impressed me, but I think his hands are so good at third that I felt like picking the ball was going to be new, but you could expect him to do it well,” second baseman Danny Espinosa said. “It’s hard to say you expect it of him because you don’t want to put that type of expectation on him, but his hands are so good that it looks pretty easy for him.”

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Zimmerman has made two errors, most recently an ill-advised throw to second against the Phillies last weekend, and has a .995 fielding percentage. The stubborn shoulder that forced him to move from third base and the sidearm throw he adopted as a result fit well at first, where throws are not often required and are usually short when they are. Zimmerman has started six double plays this season, more than any first baseman in baseball.

“His throwing has been great — on line, firm — and he’s doing the 3-6-3 as well as anybody I’ve seen,” said Nationals General Manager Mike Rizzo, who expects Zimmerman to win a Gold Glove at first base. He already has one at third.

So the basics are there, but everyone in the Nationals organization figured they would be. Metrics that measure things such as range and runs saved above the average player rank Zimmerman as the second-best defensive first baseman in baseball. Experienced players such as Mets first baseman Lucas Duda, Reds first baseman Joey Votto and injured Cardinals first baseman Matt Adams rank ahead of him in some of those categories. But Duda, for example, is in his fifth season as a big league first baseman. Zimmerman is in his second month.

Whereas in April, Zimmerman might have taken two or three false steps after an out-of-reach ground ball, he rarely has to scramble back now. When he holds runners against left-handed hitters, prone as they are to pull the ball down the line, Zimmerman does not shuffle as far to his right to get in position when the pitcher delivers. He checks in with his coaches after plays made and not made, hoping for affirmation or a quick alteration to make sure next time goes better.

“In baseball the worst term we have is ‘instinct,’ ” defensive coordinator Mark Weidemaier said. “My dogs have instincts. You have an instinct to eat when you’re born. Baseball instincts — nobody comes out of the crib knowing how to play first base. So you learn them through powers of observation, intelligence. I think his powers of observation and his intelligence and his aptitude for the game are at a high level, which allows him to pick things up quickly.”

Zimmerman said the most difficult part of the transition has been learning when to go for balls to his right and when not to. As long as pitchers understand his aggressiveness and cover first base accordingly, Zimmerman can go for balls farther to his right than most first baseman. That allows Espinosa and Dan Uggla to play farther up the middle. More ground gets covered.

“At third base you go and get everything you can,” Zimmerman said. “A lot of our pitchers are pretty athletic, can get over than and cover. But obviously you’d rather have the first baseman there. Our second basemen have good range. So once or twice I’ve gone after balls I probably shouldn’t have.”

Nationals Manager Matt Williams, who also converted from third to first, said the only way to learn the potentially complicated plays at first base is to experience them. Some things — such as learning pitchers’ pickoff moves, seeing the tail and sink on infielders’ throws and knowing when to take outs and when to take chances — require experience. Everyone in baseball lauds Zimmerman’s hands and athleticism, the unteachable prerequisites to excellent defense.

In two months’ worth of games, he has become one of the league’s steadiest first basemen. After a season’s worth, people may start to notice.