The Wizards had led with 8:40 to play, but the Nuggets went on a 9-1 run capped by Darrell Arthur's 3-pointer from the right wing to sneak in front and see out the victory.
"We aren't going to beat anybody with 24 turnovers," Wittman told reporters after the game.
"It doesn't matter who you're playing, who's playing or not playing, or where you're playing.
"In the first quarter we came out and played through our system, moving the ball and guys in the right spots. All of the sudden we're up 14 and from there it just stopped."
The loss sees the Wizards sitting in second position in the Southeast Division, with a record of 36-34 for the season.