Swiss maestro Federer, looking to regain the year-end top ranking after being overthrown by Rafael Nadal last year, dug himself out of trouble to win 4-6, 7-5, 6-1 and join Murray at the top of Group A in the season-ending showpiece.
World number one Federer was top billing for the evening session at the spectacular 02 Arena but lost his opening service game to love and sprayed 15 errors in the first set as Verdasco threatened to cause a shock.
He then survived a crisis at 5-5, 0-30 in the second set, breathing a sigh of relief as the left-handed Verdasco went agonisingly wide with a forehand -- a near-miss confirmed by a Hawkeye replay accompanied by thumping heartbeat sound effect, which was just part of the razzmatazz enjoyed by the 17,500 crowd.
Crisis over, 15-times grand slam champion Federer broke serve for the first time in the match in the following game to take the set and then raced away to victory.
Six-times Wimbledon champion Federer said he was impressed with the venue and the lighting, which leaves the crowd in virtual darkness as the players duel on a vivid blue court.
Murray withstood a ferocious comeback by U.S. Open champion Del Potro to claim a 6-3, 3-6, 6-2 victory that at one stage looked to be slipping away from him.
Del Potro, who lost the first five games, scorched some huge forehand winners but was finally undone by the wily world number four, who soaked up everything the burly Argentine threw at him. Things began to change as Del Potro found his timing to claw it back to 3-5 and, although Murray finally clinched the opener on his seventh set point, the tide had turned.
Del Potro broke serve twice in the second set and after softening up Murray with some punishing inside out forehands that Murray could merely slice back defensively he levelled the match with an unstoppable crosscourt effort. As quickly as it had sparked into life, however, Del Potro's challenge withered and world number four Murray won the third set surprisingly comfortably after breaking in the second game.
Bhupathi-Knowles win
In the doubles event, third seeds Mahesh Bhupathi and his Bahamian partner Mark Knowles beat debutants Frantisek Cermak and Michal Mertinak 6-3, 6-3 in their first Group A match. Poles Mariusz Fyrstenberg and Marcin Matkowski stunned Daniel Nestor and Nenad Zimonjic 6-4 6-4 in another Group A match.
