Nowhere is the lack of time felt more than in queen endings. On nearly every move, the players must try to visualize the consequences of an avalanche of checks.
In most endings, a player must carefully weigh the value of advancing a pawn closer to the queening square against the possibility of it becoming weak due to lack of support. Hence, the general endgame principle of pieces before pawns, i.e., unless the ending is a pure pawn race, players should try to improve the position of their pieces before they advance their pawns.
In queen endings, however, advanced pawns are much less likely to become a liability. This is because a queen has the ability to protect a pawn and control the squares in front of the pawn at the same time without hindering the pawn's advance. A king can blockade a pawn that is only supported by a knight, a rook, or a bishop, but it is helpless to stop the advance of a pawn supported by a queen. In fact, it often has to worry about being mated. Even another queen acting alone cannot hold back a pawn supported by a queen.
The flip side of the queen's ability to advance a pawn without assistance is its ability to oppose a king and a pawn without assistance. Acting alone, a knight, a rook, or a bishop has difficulty holding back a pawn supported by a king and can often be forced to sacrifice itself to prevent a pawn from queening. A queen on the other hand has very little trouble holding back a pawn by itself. In fact, it can often hold back several pawns.
The upshot of all this is that having the farthest advanced pawn is of paramount importance in queen endings. It is not unusual to see a deficit of several pawns be offset by a single pawn that has reached the sixth rank because the extra pawns can be easily rounded up if the defender can be forced to sacrifice his queen.
All of this brings us to the following position from Moskwa v. Meduri.
Fearing Black's g-pawn, Robert played 59.d7+? Qxd7 60.Qxg3 and the game ended in a draw. However, despite the fact that Black's g-pawn is as near to its queening square as the White's d-pawn, the Black pawn is not supported by its queen and the Black queen is needed to defend against mating threats. After 59.c5!, Black can't play 59...g2 because of 60.Qb8+ Kf7 61.Qb7+ Kf8 62. Qxg2. If Black tries 59...Qd7, 60.c6! is devastating.
Cross posted to Prospect Chess