Thirty minutes into game 1 of a Swiss Round between 2 control decks, Amelia finds herself with a sure, instant win (it is day 2, so she knows that Noelle has no out in her whole deck).
There is only one card in Amelia's deck that can guarantee such a instant win, and the game state is pretty much balanced otherwise.

If Amy decides to play through the motions of the game as though she did not have the win card in hand, in hopes to win the match 1-0, but without playing slowly, is that Stalling?

Nope, that's fine. Even if they have the win in their hand or on the board, they're not required to win the game. As long as they're continuing to play at an acceptable pace, they can continue playing.

We would be DQing a lot of players if “not winning a game whenever possible” was Stalling. I think it is a good thing that this is not considered to be Stalling in any way.

Edited Julien de Graat (Jan. 4, 2014 10:12:27 PM)

Just playing a little advocatus diaboli:

If we look at Amy's intention described, she isn't just playing on, because she plays bad, or she doesn't see the winning move.
She actively decides not to win the game to consume time on the clock, hoping to win the match 1:0.

Doesn't that intention perfectly fits the “USC - Stalling” Definition, does it?

We just don't DQ her because we just can't be sure about her intention.

Failing to win (or lose) the game in a Judge-appropriated “reasonable time” is not Stalling, assuming the game is proceeding at a reasonable pace. If we assume that because Player A has knowledge of Player B's deck and knows that Player B has no outs, and hence Player A should just win now, what do we do in the cases of other methods whereby Player A knows the contents of Player B's deck? As an example, consider the case where Player A casts Cranial Extraction (or another such card) and looks through Player B's deck, but doesn't take note of whether or not Player B is playing countermagic. Player A “should” know that Player B is not (we're assuming the “not” part here) playing countermagic and hence should not play around it, but Player A doesn't know that and hence we can't reasonably apply a penalty to Player A. The only difference between that situation and this one is how Player A gained knowledge of Player B's deck, and recall that players are not allowed to refer to out-of-game notes while in-game, so knowledge of decklists without being able to refer to them in-game is basically the same as using an Extract effect.

…if you wanted some sort of patchwork rationale for the answer “no”.

Originally posted by Farid Taoubi:

If we look at Amy's intention described, she isn't just playing on, because she plays bad, or she doesn't see the winning move.
She actively decides not to win the game to consume time on the clock, hoping to win the match 1:0.

Doesn't that intention perfectly fits the “USC - Stalling” Definition, does it?

IPG:Stalling
A player intentionally plays slowly in order to take advantage of the time limit.

No - it does not fit Stalling. Stalling requires that a player plays slowly, and we define slow play as “A player takes longer than is reasonably required to complete game actions”. So as long as a player is making actions at a reasonable pace, regardless of whether those actions ultimately make the game end sooner or last longer, is not guilty of either Slow Play or Stalling.

I'm going to go ahead and close this thread up now, as the original question is fficially answered, to make sure we don't go down any un-productive corners.

I feel it's worth tacking on one more comment; we don't (can't!) put judges in a position where their rulings depend on their interpretation of “the best play” or other subjective measures. It would create some very difficult situations - not to mention drastic inconsistencies.
(Obviously, investigations are a different topic.)