The Sam Querrey-Stanislas Wawrinka match is just about to hit the four-hour mark.
Wawrinka is on serve and holds a 2-1 lead in the fifth set. The winner advances to the quarterfinals.
UPDATE (5:26): Querrey is serving, down 3-2 in the fifth set.
UPDATE (5:37): Querrey is serving, down 4-3 in the fifth set.
UPDATE (5:42): Querrey has tied it up. It's 4-4.