Davydenko wore down the hard-serving Ivo Karlovic for a 6-7 (5-7), 7-6 (8-6), 6-0 victory. After winning the last three points of the second-set tiebreaker, Davydenko turned around and controlled the third set. He lost only nine points -- three on serve -- in the set.
Each player had a break in the first set and Davydenko saved five break points to keep in the second set.
Top-seeded Jo-Wilfried Tsonga, the tournament defending champion, fell behind early against Jesse Levine but won the last five games of the first set and didn't face a break point in the second of a 6-3, 6-4 win.
Seventh-seeded Gael Monfils knocked off No. 2-seeded Philipp Kohlschreiber 6-7 (3-7), 6-4, 6-4 in a 2 1/2-hour match. Monfils improved to 7-1 lifetime against the higher-rated Kohlschreiber with two breaks in each set.
Fifth-seeded Andreas Seppi took out No. 4-seeded Florian Mayer 7-5, 6-2 in 61 minutes. Seppi was broken once but still dropped just 12 points over 10 serving games.
Tsonga will go against Davydenko in the semifinal Saturday while Seppi plays Monfils.
Swim Week Miami Beach 2014 [PHOTOS]