I don't understand the current sign stealing issue between the Red Sox and the Yankees. I don't understand how sign stealing in baseball actually works. Just seeing a catcher's sign is not enough.
How can a team know what their opponents' signs actually mean?
Doesn't each team have their own signs?
Don't they change their meanings now and then like a password?
The Boston Globe quotes Red Sox second baseman Dustin Pedroia:
Our adjustment to that stuff is: go out to the mound and change the signs.
OK, I guess one could identify the current signs at the start of a game by watching the signs and the pitches that follow. Yahoo describes this process:
if someone on a team’s video staff cracks an opponent’s signals, they are run from the video room to an intermediary in the dugout and forwarded to players on the field
But that process would take longer than the actual at bat itself and the information would never reach the batter in time. The only benefactor would be the runner at second base who will know when to steal a base. But he should be able to see the catcher's signs directly and wouldn't need a relay chain.
Of course, that runner could alert the batter directly on what pitch to expect once the signs have been cracked. The Boston Globe describes this:
Often times it happens when a runner at second base peers in to see the catcher’s sign and then subtly flashes a signal — maybe a hand movement, or the positioning of his feet — to the batter to let him know whether the next pitch will be a fastball, curveball or something else.
But how often is there a runner at second base during a game? It's not that big of an advantage in my opinion. And I'm pretty sure all teams have been doing this for 150 years or so.
Disclaimer: I have never played baseball myself, unfortunately. I'm just an interested spectator so please bear with me.