Foggy morning here in Viera, where it was Photo Day, the annual rite where players bounce from station to station, posing for video board headshots and card companies and newspaper shutters. They wore game uniforms, and the unlucky ones had to arrive around 6 a.m. “It feels like I’ve been here for six hours,” one player observed as the 9:15 a.m. team meeting neared.

The Nationals will focus on defense today after a rainstorm washed out their drills yesterday. Manager Matt Williams has emphasized defense so far in camp, but he has had his hands with plenty of tasks, including learning how to use instant replay.

On Friday afternoon, Matt Williams drove an hour or so to Kissimmee in order to meet with Joe Torre and other MLB officials about baseball’s new replay system. The Nationals contingent also included bench coach Randy Knorr, defensive coordinator Mark Weidemaier, video coordinators Erick Dalton and Chris Rosenbaum and assistant GM Bryan Minniti. Managers and officials from three other teams – Detroit, Atlanta and Houston – attended as well.

The meeting lasted for about two and a half hours, but it could have gone on forever. The answer to every question with the new system tends only to lead to more questions. Here are some of the highlights from what Williams gleaned:

** Managers will start the game with one challenge, which can only be used in the first six innings – from the seventh on, umpires must initiate all replay challenges. If the manager wins his challenge, he is rewarded with another challenge.

** Not every call can be challenged, even within the realm of plays that in most circumstances can be challenged. For example, fair-or-foul calls can be challenged. But balls that bound down the line and over a base are not challengeable.

“Because they simply don’t have angles to cover that,” Williams said. “They’d have to put a camera everywhere within the ballpark to cover those. So some of those, they just can’t see. Or they can’t see effectively enough to make a ruling. So that’s an example. There’s a number of them.”

Another example: the famed “neighborhood play,” when a shortstop or second baseman gets credit for being close to second on a double play even if he is not touching it, can be replayed – but only if a throw carries the fielder away from the base. A routine turn with a second baseman’s foot an inch off the bag cannot be overturned. But umpires can rule a poor throw forced a fielder to move an inch off the bag. At least that was Willams’s interpretation. That’s a tricky one.

** The timing was a big issue in the meeting.

“Without getting too detailed about it, if a play happens, and one manager decides to go make a pitching change, the other manager that wants to challenge from the other dugout must do that before the game leaves the bullpen,” Williams said. “So that’s timing. If it’s a play that ends the game, it must be done immediately. There’s differences depending on what play it is and what time of the game it is, there’s differences in how you must challenge, and what kind of time frame that takes.”

** In order to challenge a call, the manager simply walks to the field and asks – there are no challenge flags or buzzers or anything like that. Managers can ask a particular umpire for a challenge – the third base ump on a foul-fair call in left field, for example – but are encouraged to go to the crew chief.

What’s fascinating: Managers can still argue a call without asking for it to be challenged. They can even prod umpires to confer and challenge it on their own. Managers cannot ask for replay after the seventh, but umpires can ask for replay in the first six innings.

“You’re not restricted from going out and arguing, which is good,” Williams said. “It’s not like you just have to throw the flag, or walk out to the crew chief, or whatever. You can still go defend your player, or whatever it is, and then have the ability to also challenge.”

** Managers are allowed to walk to the field without knowing if they will challenge. In every major league dugout and clubhouse area, a team employee – the Nationals will use their video coordinator – will have access to a monitor that shows the same live feed that the central league office will use to review challenged calls. That employee has a phone line to the dugout. A manager can look over his shoulder and get a signal for whether he should challenge or not while arguing with the umpire.

Williams and the rest of the managers will receive a full book of rules and regulations for the replay system. The meeting provided a basic understanding, but there are so many nuances and what-ifs that it will take a while to understand the system in full.