Wizards forward Otto Porter Jr. battles with Mavericks guard Wesley Matthews during Dallas’s 113-99 win. (Toni L. Sandys/The Washington Post)

During a rough stretch for the Washington Wizards in a game that was full of them, a fan inside Capital One Arena pleaded with his home team.

With the Wizards trailing by double figures Tuesday night, a shout of "Wake up!" could be heard in the otherwise quiet lower bowl. This cry didn't arouse the Wizards from the nightmare of losing to the worst team in the NBA.

The Dallas Mavericks led throughout their 113-99 win over their listless hosts. Harrison Barnes joined the expanding club of scorers to have charred the Wizards — the Phoenix Suns' T.J. Warren and Cleveland Cavaliers' LeBron James are charter members this season — as he poured in a game-high 31 points. Dallas rookie Dennis Smith Jr. added 22 as Washington (5-5) took yet another head-scratching loss to a beatable Western Conference team after previous letdowns against the Los Angeles Lakers and Suns.

"We keep talking about being a defensive team, but now it's actions," Wizards Coach Scott Brooks said. "We've got to be an action-defending team, and right now we're not doing that. In order to win in this league consistently or to give yourself a best chance, you got to do it. I got to figure out a better way to get guys on the floor to be active on the defensive end and not worry about their shots."

Wizards guard John Wall, who sat out Sunday's game, returned to the floor with black therapeutic tape over his sore left shoulder. The protection did not temper Wall's bursts. Every trip to the rim and hard landing raised gasps and groans throughout the arena, but they were not in vain as Wall made 13 of 18 free throws as part of his 23-point, 14-assist night. Wall made eight straight free throws early on, but he missed a critical pair as the Wizards trailed by eight with 3:27 remaining in the game.

Until the end, Dallas (2-10) stayed in control and made the Wizards repeat the same pledges to do better they have recited throughout the inconsistent season.

"I'm probably sounding the same trying to tell you something different, but it's the same thing over and over," said Wizards guard Bradley Beal, who scored 23 points on 8-for-20 shooting and finished as a minus-15. "We developed a bad habit of not coming out with energy. I'm taking it on my shoulders. I got to do a better job of defending and getting the bench going, and it starts with me and John. We got to come out better, be better leaders on the team, and the rest with follow. Overall, our defensive effort is not there. We keep worrying about offense, and offense isn't a problem. It's our defense."

The Wizards had careless moments with the ball, giving away nine possessions for 12 points in the first half. But their offense rarely deserves blame. Scoring is not the issue, as the Wizards' 61.1 percent shooting in the first quarter proved. As usual, the Wizards' defense failed them — even during what should have been a gift-wrapped game.

Playing Dallas, which entered the night with the worst record in the league, should have represented a chance for Washington to spruce up its defensive stats. Washington had allowed 109.2 points per game entering Tuesday, but Dallas countered those poor numbers with pathetic ones of its own. The Mavericks ranked 28th in the league in scoring and had not broken 100 points in their previous four games — all losses.

Yet Washington could not even stop this team.

Fifteen seconds into the game, Smith slammed down with an emphatic alley-oop dunk, and that was followed by 39-year-old Dirk Nowitzki's layup. Besides these easy buckets, the Mavericks also stretched the floor and hit five of their first eight shots from beyond the arc. Afterward, Brooks called out each starter by name while delivering a message for improved first-quarter efforts.

"It's going to be the same message from me, and the players are going to continue to hear it," Brooks said. "We have to be a defensive team that can score, and not a scoring team that can play defense when we score. It just has to be that way."

Tuesday's defensive effort didn't immediately harm Washington. After all, the Wizards' starters can score with any unit in the league, and after the first quarter, with both teams shooting over 60 percent, the Wizards trailed only 36-34. Eventually, though, this aversion to defense created a problem.

Unlike the starters, who can sometimes cover their defensive mistakes with offensive intelligence, the Wizards' bench players are seeking a rhythm. On Tuesday, the unit remained lost.

Jodie Meeks missed his four shot attempts early in the second quarter and returned to the bench by striking the last chair, but at least he showed a pulse on the offensive end. Point guard Tim Frazier and center Ian Mahinmi played more than half of the quarter without attempting a shot. Mike Scott accounted for the unit's only points during its first appearance.

While the Wizards' bench struggled, Dallas opened the quarter on a 9-0 run and soon Brooks began to rotate starters back in.

Washington may not have solved its defensive dilemma — for three quarters, Dallas scored at will in building a 90-76 lead — but the team might have found a stopgap for the second unit. As the Wizards made a fourth-quarter comeback, Otto Porter Jr. played alongside four bench players and resuscitated the group.

The Wizards scored 12 straight points to pull within two with under nine minutes to play. Ultimately, though, they could not finish.

"Oh, we do this every year," Wall said of the poor defensive start. "Until we lock in and figure it out, and everybody takes pride in guarding one-on-one, and if somebody gets beat, you help the helper and make extra efforts, we're going to deal with the same problems."