For the Washington Wizards, Sunday’s loss to Indiana in Game 4 of their Eastern Conference semifinal playoff series was not so much shocking as it was sobering.

The Wizards were riding high during the first half Sunday en route to a 17-point advantage, but they had seen double-digit second-half leads evaporate before — 11 other times this season, in fact. They also had witnessed passes bobbled away like the one from Trevor Ariza that sailed wide in the final moments, replaying a scene that left the Wizards tied for last in the NBA for average turnovers (0.9) in the final three minutes of a game.

This time, though, those mental lapses of old placed the Wizards on the brink of elimination from their first postseason in six years. With a loss in Tuesday’s Game 5 at Indiana, the Wizards’ postseason run would end after they held a 1-0 series lead on the Pacers a little more than a week ago.

“It’s tough, man. We really did put ourselves in position to win,” said Wizards reserve forward Al Harrington, who had 11 points in Sunday’s loss. “It’s upsetting when you come up short. Play here, play there could’ve been the difference in us winning. But I guess that’s just part of this team still growing.”

Less than two weeks ago, the Wizards appeared to have forged past their growing pains. Against a Chicago team that posed a defensive challenge similar to Indiana, the Wizards were clicking in a way they hadn’t experienced consistently since February, when they won a season-high six straight games.

The Post Sports Live crew looks at the Wizards' victory over the Pacers in Game 1 of the NBA playoffs second round and debates whether Washington can win the series. (Post Sports Live/The Washington Post)

In that first-round series, their turnover average fell from 14.7 to 10.4 per game, their number of assists increased by nearly three a game behind sound ball movement and they had Nene. After missing 22 games because of a sprained ligament in his left knee, the Wizards forward was putting together the best playoff performance of his career, knocking down midrange jump shots while frustrating Defensive Player of the Year Joakim Noah.

Since then, the Wizards have seen their turnovers spike back to an average of 14.8 while their third-quarter offensive rating now sits at just 83.6 points per 100 possessions in the playoffs.

“You can say it’s mental, but it’s something that we definitely can’t say we can work on,” Wizards forward Drew Gooden said. “We’ve got to figure it out ASAP because we ain’t got too much leisure time to try and figure out what’s wrong with us in the third quarter, so we got to try to figure it out now.”

The Wizards initially appeared to exorcise those demons toward the end of the regular season, when they won their final four games, but they admit that adjusting on the fly during a playoff series presents a different challenge. Player tendencies have been exposed, most strategies have been exhausted and, for the Wizards especially, the stakes are now critical.

“As I told them, we know what we have to do. You played them four different times. This will be the fifth game coming up. There isn’t any secrets,” Wizards Coach Randy Wittman said. “We’ve got to go back to Indy, and we’ve got to get one game. We’ll worry about Game 6 after Game 5. Three of the four games have been a dogfight. We’re in the fight; now we’ve just got to win the fight.”