DALLAS -- Luka Doncic, who is in the midst of the most prolific scoring run in Dallas Mavericks history, couldn't have asked for a better look with the game on the line Sunday night.

And he couldn't believe he didn't make it, clutching his temples with both hands and staring at the American Airlines Center rafters after his wide-open 3-pointer from the left wing rimmed out with five seconds remaining to seal a 121-118 loss to the Portland Trail Blazers.

"It doesn't matter if I'm confident or not. The shot went out," said Doncic, who had 44 points on 14-of-20 shooting and nine assists in the loss. "Obviously, I was disappointed. I thought it was in, and it went in and out, so I was disappointed. That's on me. I should have made the shot."

Doncic isn't missing much lately. His 90 points over the weekend -- he had a career-high 46 in Friday's win over the New Orleans Pelicans -- are the most in a two-game span in franchise history. He shot 62% from the floor in the pair of games, including 5-of-8 from 3-point range in both contests.

The Trail Blazers didn't want to let the Mavs attempt a shot at all on the possession, much less give Doncic a good look, as Portland planned to take a foul to send Dallas to the free throw line. However, Doncic came free after getting a screen from Kristaps Porzingis and got off an uncontested shot that would have tied the score.

"If he had that shot nine more times, I think he'd make it nine in a row," Mavs coach Rick Carlisle said. "I mean, it was in and out. And that's the guy we want to take it. I thought that was a great look, so we're disappointed."

Dallas rallied from a dozen-point deficit in the fourth quarter, tying the score with 49.5 seconds left when Dorian Finney-Smith made a 3 off a Doncic feed. But Portland superstar Damian Lillard gave the Blazers the lead for good on the next possession, adding to his extensive collection of clutch buckets by swishing a stepback 3 over Finney-Smith.

"He sat down in his stance like he was going to have a good possession on defense," said Lillard, who had 34 points and 11 assists. "It's what you expect from defenders in this league, but I noticed that they weren't going to double, and I was like, 'It's going to be a 1-on-1.' I got the shot that I wanted. I got a clean look. In my mind, I was like, 'All right, if this is what it's going to be, I'm fine with this.'"

Finney-Smith was left alone on Lillard at the top of the arc because Dallas didn't execute the game plan. The Mavs' coaches called for a double-team, according to Carlisle, wanting to get the ball out of Lillard's hands.

"The communication didn't get there," Carlisle said. "He hit a difficult shot, but it's a shot he makes regularly."

Nobody in the NBA hits more shots in those situations than Lillard. According to ESPN Stats & Information research, this was his 33rd career go-ahead basket in the final minute of a game, including the playoffs, the most in the league since Lillard was drafted in 2012.

Lillard also leads the league this season with 65 points in clutch time, which is defined as the final five minutes of regulation or overtime when the score is within five points, shooting 58% from the floor in those situations. He had seven of Portland's nine clutch points Sunday.

"He's done it for a long time," Portland coach Terry Stotts said. "A lot of times, the most important thing is just getting him the ball. That's what great players do. They make those plays, and obviously he is a great player."