Johnson's role grew in his second NBA season, as his 28.5 minutes per game surpassed his rookie mark by over 10 minutes per contest. Not surprisingly, he posted substantial gains in production. Johnson averaged 12.8 points, 6.0 rebounds and 1.8 assists for the Spurs while playing in 69 games. He made 47.9 percent of his attempts from the field and 74.0 percent of his free-throw tries. The sophomore forward started all but two of the games in which he played and logged at least 20 minutes in all but one contest. He notched eight double-doubles during the campaign, including a March 19 performance against Cleveland during which he scored 23 points and grabbed a career-high 21 rebounds. Johnson posted a number of other single-game career highs during the season. He collected three blocks against Minnesota on Jan. 10, then registered another career-best with 29 points versus Houston four days later. On Feb. 9, he tallied six assists against Golden State to set another career-best mark. Johnson was effective in the Spurs' play-in loss to Memphis on May 19, finishing with an 11-point, 11-rebound double-double.2019
After being selected by San Antonio with the 29th pick of the 2019 NBA Draft, Johnson went on to spend the majority of his season in the G League with the Austin Spurs, though he also ended up making 17 NBA appearances (one start). Johnson appeared in 31 G League games, averaging 20.3 points, 5.6 rebounds and 2.4 assists over 30.2 minutes. His best G League performance came Dec. 17, when he posted 32 points, four three-pointers, eight rebounds and two assists against the Herd. On Feb. 25 with Austin, the 6-foot-5 wing generated 31 points, three rebounds, two dimes, two steals and one block against Sioux Falls. Johnson scored 20 or more points in 17 of his 31 G League appearances. Johnson rejoined the Spurs for good in March and ended up seeing a far larger role once the NBA resumed play in the Orlando bubble. On Aug. 5, he posted his first career 20-point game, shooting 7-of-10 from the field and adding six rebounds. Six days later, Aug. 11, Johnson set two new career bests with 24 points and 11 rebounds against Houston -- his first NBA double-double. He then closed out the season with another 24-point effort against Utah on Aug. 13.