Nalbandian, the No. 10 seed, opened the day with a third-round 4-6, 7-5, 6-3 victory over Edouard Roger-Vasselin despite 14 double faults. He had four breaks, needing two to win the second set and one to take the lead in the third.
Nalbandian came back in the quarterfinals for a 4-6, 7-6 (7-2), 6-4 decision over Xavier Malisse. He had 10 aces and won a healthy 91 percent of the points when he got his first serve in. He saw just one break point in the second and third sets.
Nalbandian, who played a total of 4 hours, 13 minutes, will go against Grigor Dimitrov in Saturday's semifinals. Dimitrov got by ninth-seeded Kevin Anderson 4-6, 6-4, 6-3.
Sixth-seeded Marin Cilic moved into the semis after he built a 6-4, 2-0 lead and Lu Yen-Hsun retired. Lu, like Nalbandian, needed to play a third-round match earlier in the day. He beat third-seeded Janko Tipsarevic 6-3, 2-6, 7-6 (7-5) but the tight match took more than 2 hours.
Sam Querrey also claimed a three-set win, topping Ivan Dodig 7-5, 3-6, 6-3 with a 2-1 edge in breaks.
Nalbandian and Dimitrov will be paired against each for the first time. Cilic came away a five-set winner at Wimbledon in 2009, the only time he's played Querrey.