WASHINGTON — After another goalie interference call went against the Lightning in a 4-2 loss to the Capitals on Saturday, coach Jon Cooper nearly popped off the bench."I feel like we're writing the book on it, and I don't know what the right answer is," Cooper said. "Because it's a different explanation every time. So it's really, really frustrating."Captain Steven Stamkos thought he had given Tampa Bay a 1-0 lead — and momentum — midway through the first period, but his goal was waved off after referees ruled Ryan Callahan interfered with goalie Braden Holtby, who was sprawling outside the crease.Sure, that hurt. But the biggest culprit in the loss — the third in four games for Tampa Bay — was the struggling power play, which failed to cash in on two minutes of a five-on-three in the second period. Capitals center Nicklas Backstrom scored two of his three goals in the next 10 minutes, and Washington held off a late Tampa Bay flurry. The Lightning power play is in a 4-for-28 funk."Obviously (the five-on-three) was the big momentum-changer in the game," defenseman Victor Hedman said. "If we put one in there, it's a totally different game."The Lightning (19-9-3) shut out the Capitals' top-ranked power play in four opportunities, including two in the first eight minutes. Then Stamkos scored after a great play by Valtteri Filppula, who circled the net and drew Holtby out of position before feeding Stamkos in front. Stamkos put the puck in an empty net. At the same time, Callahan, with Washington defenseman Brooks Orpik on his back, ran into Holtby. When asked if he was pushed, Callahan said he didn't know. "It happened quickly."But Cooper's point was that even if all the other players were taken out of the equation, Holtby wouldn't have been able to recover in time as it was. "I don't know how that's not a goal," Cooper said. Said Stamkos: "I don't know what 'Cally' is supposed to do there."The Lightning outshot Washington 5-0 early in the second before getting that five-on-three power play seven minutes in. Its best chance came when Callahan got a piece of a rebound in front, but Holtby made a spectacular save, reaching back with his stick to stop the puck before it crossed the line. The crowd roared, chanting "HOLT-BY!" and Backstrom scored two minutes later. "That was a huge kill," Backstrom said.The Lightning, which scored twice in the final five minutes to make it interesting, believes it has played well in spurts in its 1-3 stretch but not consistently enough, especially on the power play. Said Stamkos: "Our PP kind of let us down (Saturday)." Capitals 0 2 2 4 Lightning 0 0 2 2 Capitals 0 2 2 4 Lightning 0 0 2 2 First — None. Penalties — Morrow, TB, major (fighting), 1:41; Wilson, Was, major (fighting), 1:41; Drouin, TB (tripping), 4:04; Killorn, TB (holding stick), 7:27; Callahan, TB (slashing), 16:39. Second — 1, Wash, Backstrom 6 (Wilson, Schmidt), 10:33. 2, Wash, Backstrom 7 (Ovechkin, Wilson), 18:40. Penalties — Green, Was (slashing), 2:43; Ovechkin, Was (roughing), 6:49; Green, Was (hooking), 6:49; Paquette, TB, double minor (roughing), 14:20; Fehr, Was (roughing), 14:20; Carlson, Was (hooking), 19:57. Third — 3, Wash, Backstrom 8 (Ovechkin), 2:17. 4, TB, Johnson 9 (Carle, Kucherov), 15:36. 5, TB, Carle 3 (Stamkos, Garrison), 17:29. 6, Wash, Fehr 6 (Carlson), 19:21 (en). Penalties — None. Shots on Goal — TB 2-14-12—28. Wash 12-10-6—28. PP opportunities — TB 0 of 4; Wash 0 of 4. Goalies — TB, Bishop 16-6-2 (27 shots-24 saves). Wash, Holtby 12-7-4 (28-26).