Shanghai, Nov 17: Nalbandian, Roddick and Croatia's Ljubicic all ended 1-2, with Nalbandian having the best percentge of sets won.
The night started badly for the fifth-ranked Roddick, who was broken in the opening game and again in his third.
Nalbandian kept up the pressure in the second set, breaking Roddick in the seventh game on consecutive errors from the American.
But he admitted getting nervous when serving for the match, Roddick breaking back to level at 5-5 after getting breakpoint on the 24-year-old Argentine's double-fault.
In the tiebreaker, Roddick wasted a mini-break at 3-1 and then had a double-fault _ his first of the match _ to give Nalbandian a 5-3 cushion.
Nalbandian set up match point with an overhead winner and closed when Roddick netted a return.