(AP Photo/Alex Brandon)

Barring a surprise change of plans, Ryan Zimmerman is coming back to Nationals Park tonight, and he’s playing left field. One of the best third baseman in the majors for nearly a decade, and a player in the first year of a $100 million extension, is changing positions on the fly. He may play third base again, but suddenly, he is no longer a third baseman.

And that may not even the most delicate part for Manager Matt Williams. Or General Manager Mike Rizzo.

The process of moving Zimmerman around the diamond produces so many ripples in so many directions. The most immediate question is, how much is Zimmerman going to play in left? No one has an answer, not even Zimmerman. But he seems to believe it might just be on an everyday basis until Bryce Harper returns, which should happen in early July.

“I don’t know,” Zimmerman said. “I haven’t really talked to Matt or Mike or anyone about that. Obviously, Bryce is going to be out for a little while longer. We’ll see what happens when I get up there and see what they say. I’m ready to play wherever they want me to play.”

Once Harper returns, the calculus becomes especially tricky for Williams. He has said left field, third base and first base are all “options” for Zimmerman. (He also said two weeks ago that Zimmerman was getting fly balls in left field for “conditioning.” Let’s remember to take public pronouncements regarding the situation with a grain of salt.)

Zimmerman’s defensive whereabouts upon Harper’s return is a cross-that-bridge situation for the time being. Will another injury arise? Which hitter will go cold? Which will be  hot? How does Zimmerman look in left field? All those will factor into Williams’s decisions.

But assume the Nationals stay healthy, Zimmerman plays left to a draw and individual performance remains roughly status quo. There is no perfect way to Zimmerman to fit into the lineup without potentially ruffling feathers or sacrificing some attribute.

If Zimmerman plays left field, that means Harper would move to center and Denard Span would sit. (On some days, it could mean Harper plays right and Jayson Werth gets a day off, but Werth obviously means more to the lineup than Span.) Span is the Nationals’ best defensive outfielder by a lot, his bat has been coming on recently and he’s even been stealing more bases. He’s been an everyday player for years. How would he respond to frequent benching? Span has a wonderful disposition and a team-first attitude, but he would be faced with a foreign, awkward situation. Harper, on the other hand, would love to play center field. It’s by far his favorite outfield spot – his offensive numbers have even been better in center than either corner spot.

If Zimmerman plays first, that means Adam LaRoche would sit. LaRoche has been the Nationals’ most productive hitter this season. So aside from a once-a-month day off against a tough lefty, that’s a non-starter.

If Zimmerman plays third, that means Danny Espinosa would sit and Anthony Rendon would move to second base. The Nationals would give themselves their best possible lineup. But their infield defense would suffer greatly. Zimmerman’s shoulder will not let him play third on a consistent basis – that’s the whole reason he’s playing left, of course. Espinosa is the Nationals’ best defender, full stop. Rendon is better at third than second.

It will be Williams’s job to sort all of that out while keeping everyone happy and giving the team its best chance at success on a daily basis.

It will Rizzo’s job to gauge how Zimmerman’s position change should affect the future of the roster.

Span could become trade bait if Zimmerman turns out to be average or above average in left. Span’s a good player, but where would they put him? Span has an affordable, $9 million option for 2015, which makes him a desirable asset to be kept or traded.

If Span gets dealt this season, it may leave the Nationals thin in center if Harper suffers an injury. Rival scouts haven’t been impressed with Brian Goodwin’s development at Class AAA Syracuse. Michael Taylor’s bat, though scorching in Class AA Harrisburg, is not quite ready for the majors, rival scouts believe. But he would probably be an adequate fill-in based on his plus defense alone.

But if the Nationals were to move Span, they would have to answer the related question of who plays first base in 2015. Without Span, Zimmerman becomes the left fielder, not the first baseman. The Nationals and Adam LaRoche have a mutual option worth $15 million. Mutual options almost never get picked up, but this could be the unique situation where it works out: LaRoche could pull in more than a qualifying offer would net for one year while playing in a place he feels comfortable, and the Nationals would get a stop-gap season from a player they know, trust and like with no long-term risk.

And then 2016 could be the season Zimmerman – or maybe Werth at age 37? – moves to first base. Taylor or Goodwin figure to have emerged by then.

These are all remote issues to be considering now. But they are also the kind of things you start thinking about when a franchise player changes positions during the span of a disabled list stint.

Nationals beat writer Adam Kilgore talks about whether Ryan Zimmerman will eventually return to third base when he rejoins the team. (Post Sports Live/The Washington Post)