Barton's season got off to a difficult start, as he fell awkwardly during a lay-up attempt in the second game of the season, straining his groin and right hip in the process. Initially billed to miss between 5-and-6 weeks, Barton missed longer than predicted, ultimately returning on Jan. 12th in a 102-93 loss to the Suns. He finished that game with six points, five rebounds and three assists in 16 minutes. Barton quickly re-established himself in his starting role, topping 20 points seven times throughout the remainder of the regular season. He also picked up at least five assists in 10 of his 43 appearances, and he grabbed at least five boards in 20 of his showings. Defensively, "The Thrill" picked up at least one steal in 15 games and at least one block in 18 contests. He also had one double-double on the year, a 21-point, 11-board effort during a Feb. 28 home loss to Utah. Arguably his best game of the season came during a six-point loss to the Jazz on Jan. 23, with Barton posting 22 points on 8-of-13 shooting, nine rebounds, five assists, one steal and one block in 30 minutes. In 14 playoff games, Barton averaged 9.1 points, 4.8 rebounds and 1.7 assists across 23 minutes. He had a 22-point outburst during a second round Game 3 loss to Portland, which also included nine rebounds, three assists, three blocks, and two steals. Denver would ultimately be eliminated by Portland in seven-games.

Barton started nearly half of Denver's contests (40) while playing in a career-best 81 games. He played 33.1 minutes per night while logging more than 40 mins on 12 separate occasions. He set career-high marks in virtually every offensive category. Barton was one of just 15 players across the league to average at least 15.7 points, 5.0 rebounds, 4.0 assists and 1.0 steal. He shot a career-best 45.2 percent from the field and hit at least 80 percent (80.5) of his free throws for the third time in the past six seasons. Barton finished the season particularly strong. The Memphis product averaged 20.2 points over Denver's final 12 games while shooting 41.0 percent from downtown. Included in that stretch were a pair of double-doubles. Barton's 37 points in a win over the Bulls on November 30 were the most he has ever scored in a single game over the course of his first six NBA seasons. It was one of his two 30-point efforts of the 2017-18 campaign.

In his second full season with the Nuggets, Barton appeared in 60 games and made 19 starts. In 28.4 minutes per game, he averaged 13.7 points, 4.3 rebounds, 3.4 assists and 0.8 steals while shooting 44.3 percent from the field and a then-career-best 37.0 percent from downtown. Barton missed a combined 17 games due to left ankle and foot injuries. On opening night against the Pelicans, Barton recorded 22 points, five rebounds and two assists. He scored a season-high 35 points in a win over the Clippers on March 16, adding five rebounds and three assists. In a win over Dallas on Feb. 6, Barton had 31 points, eight rebounds, five assists and two blocks. In a Feb. 13 win over Golden State, he tied his season-high of 10 rebounds to go with 24 points and seven assists. He recorded a season-best eight assists on two separate occasions, including in a win over the Lakers on Jan. 17 when he also chipped in four rebounds and 26 points. On the defensive end, Barton recorded at least one steal in 33 games and at least one block in 23 games.

The Memphis product appeared in 82 games for the Nuggets, making one start and averaging 28.7 minutes. He posted averages of 14.4 points, 5.8 rebounds, 2.5 assists and 0.9 steals. Barton shot 43.2 percent from the field, 34.5 percent from three and 80.6 percent from the free throw line. Barton scored in double-figures 60 times, including 20 games with at least 20 points. He topped out with 32 points, to go with 10 rebounds and six assists, in a loss to the Pelicans on Dec. 20. Barton went for 31 points in a loss to Portland on Dec. 30. He recorded 21 points, 13 rebounds, a season-high seven assists, and two steals against the Warriors on Jan. 2. In a win over the Knicks on Feb. 7, Barton went for 19 points, 11 rebounds, five assists, one steal and one block in 29 minutes. He scored in double-figures in every game from Nov. 27 through Jan. 2 (19 games), averaging 19.4 points, 7.3 rebounds, 3.2 assists and 1.0 steal during that span. At season's end, Barton finished fourth in the voting for the NBA's Sixth Man of the Year award. He received 15 of 118 first-place votes. Barton also finished fifth in the voting for the league's Most Improved Player award, garnering one first-place vote.

Barton split the season between the Trail Blazers and the Nuggets, appearing in 58 total games. He began the year in Portland, where he suited up for 30 contests. In 10.0 minutes per game, Barton averaged 3.0 points, 1.1 rebounds and 0.9 assists per contest for the Trail Blazers. On Feb. 19, Barton was traded to Denver in a deal that brought Arron Afflalo to Portland. Barton stepped into a larger role with the Nuggets, with whom he logged 24.4 minutes per game and posted averages of 11.0 points, 4.6 rebounds, 1.9 assists, 1.2 steals and 0.5 blocks per game. Barton hit 44.3 percent of his field goals and 28.4 percent of his threes in a Nuggets uniform. He debuted for Denver on Feb. 22 and posted eight points, three assists, two steals and a block during a loss at OKC. Two games later, Barton scored 22 points, to go with eight rebounds and three assists in a loss to Phoenix. On Mar. 1, he posted his first double-double of the season via 16 points and 10 rebounds in a loss to New Orleans. He matched that rebounding total, with 12 points and two assists, in a win over Utah on Mar. 27. On Mar. 15, the Memphis product scored a season-high 25 points in a win over the Pelicans.

In his second NBA season, Barton appeared in 41 games for Portland and averaged 4.0 points, 1.8 rebounds and 0.8 assists in 9.4 minutes per contest. He hit 41.7 percent of his field goals, 30.3 percent of his threes and a career-high 81.3 percent of his free throws. Barton made his season debut against the Nuggets on Nov. 1, playing one minute off the bench. He scored his first points of the campaign against Golden State on Nov. 23, finishing with two points (1-1 FG) in a 12-point victory. Barton recorded at least one steal in eight games, and he had a season-high two steals against the Sixers on Dec. 14. The Memphis product recorded a pair of double-doubles on the season, including a 20-point, 11-rebound outing in a win over the Nets on Feb. 26. He handed out a season-high four assists on three separate occasions. Against the Clippers on Apr. 16, Barton had 23 points (3-7 3Pt), 10 rebounds, two assists and one steal. Barton appeared in seven of Portland's 11 playoff games. During the Game 4 win over the Spurs during the Western Conference Semifinals, Barton posted 17 points, six boards, two assists and one three-pointer over 29.5 minutes of run.

A second-round pick in the 2012 NBA Draft, Barton made an immediate impact in Portland. As a rookie, he appeared in 73 games and made five starts. In 12.2 minutes per contest, Barton averaged 4.0 points, 2.0 rebounds, 0.8 assists and 0.5 steals. He made his NBA debut against Oklahoma City on Nov. 2, finishing scoreless in one minute of action. Barton recorded his first NBA points one night later when he went for five points (2-7 FG), four rebounds, one assist, one steal and one block in a win over Houston. Against Dallas on Apr. 7, Barton posted 22 points, 13 rebounds, six assists and three steals (all career-bests). He became the first player to achieve that line off the bench since Cliff Robinson in 1993 and the first rookie to record at least 22 points, 13 rebounds, six assists and three steals since Grant Hill in 1995. Late in the season, Barton moved into the starting lineup for the Blazers' final five games. In that span, he averaged 15.2 points, 6.0 rebounds, 3.2 assists and 1.4 steals in 38.0 minutes. In the second-to-last game of the season against the Clippers on Apr. 16, Barton posted 17 points, six rebounds, five assists and three steals.