Mike Ribeiro also scored for the Stars, who won their fifth consecutive game. Dallas goaltender Andrew Raycroft was strong with 37 saves.
Mike Knuble scored the lone goal for Washington, which saw its four-game win streak halted. Michal Neuvirth allowed two goals on 21 shots in the loss.
Only 20 seconds after Knuble’s power-play tally knotted the score, the next shift saw Segal put Dallas in front for good.
Brenden Morrow held control along the left half-wall in the neutral zone and fed a lead pass to Segal, who skated to the top of the right circle and released a floating wrister that beat Neuvirth to the upper far corner with 9:22 to play in regulation.
With seven seconds remaining, the Caps thought they tied the score, but the referee immediately ended Washington’s celebration when he waived his arms to nullify the play due to goaltender interference.
The Stars have won seven of their last nine overall against Washington.
Following a scoreless first period, the Stars opened the scoring with a power- play goal at the 13:29 mark of the second stanza. James Neal controlled behind the net and passed into the right circle for Brad Richards. Richards quickly sent the disc toward the net and it deflected amongst skates and sticks in front before Ribeiro found the loose puck and punched it home for a fairly easy rebound tally from in close.
Matt Niskanen was whistled for hooking at 8:22 of the final stanza and the Caps went to work with the extra skater. With only four seconds remaining on the power play, Knuble’s one-timer from the bottom of the left circle — off a cross-ice feed from the right side by Mike Green — lit the lamp.
Raycroft made 14 saves in the first period…Dallas was 1-for-6 on the power play, while the visitors were 1-for-3 with the extra skater…It was the fourth goal of the season for both Ribeiro and Knuble. Segal’s tally was his third of 2010-11…Dallas moved into sole possession of first place in the tight Pacific Division, two points ahead of both Phoenix and Anaheim.