Island (2016–2017) On December 10, 2016, Ferrell was reacquired by the Long Island Nets. Dallas Mavericks (2017–2018) On January 28, 2017, Ferrell signed a 10-day contract with the Dallas Mavericks. He made his debut for the Mavericks the following day, recording nine points and seven assists in 36 minutes as a starter in a 105–101 win over the San Antonio Spurs. A day later, he scored a then career-high 19 points in a 104–97 win over the Cleveland Cavaliers. On February 1, in a 113–95 win over the Philadelphia 76ers, Ferrell had 11 points and five assists in 38 minutes in just his third game with the team. Two days later, he scored a career-high 32 points in a 108–104 win over the Portland Trail Blazers. He became just the third undrafted rookie in NBA history to have a 30-point game within his first 15 games, joining Connie Hawkins (twice) and Anthony Morrow. Ferrell, a 28 percent 3-point shooter coming into the game against Portland, hit nine three-pointers on 11 attempts, which tied the record for made three-point shots in a game for an NBA rookie. On February 7, 2017, he signed a multiyear deal with the Mavericks. Deron Williams' return from injury on February 11 against the Orlando Magic meant Ferrell didn't start at point guard for the first time in eight games since joining the Mavericks. Despite coming off the bench, he was solid again with 10 points and seven of Dallas' season-high 32 assists in a 112–80 win. On March 2, 2017, he was named Western Conference Rookie of the Month for games played in February. He led all Western Conference rookies in scoring (12.0 ppg), assists (4.7 apg) and minutes (31.5 mpg) in February. At the season's end, he was named to the NBA All-Rookie Second Team. On December 22, 2017, Ferrell scored a then season-high 23 points in a 113–101 loss to the Miami Heat. On January 10, 2018, he made seven 3-pointers and scored 22 points in a 115–111 win over the Charlotte Hornets. On March 6, 2018, he scored a season-high 24 points with six 3-pointers in a 118–107 win over the Denver Nuggets. On June 26, 2018, Ferrell received a qualifying offer from the Mavericks. They later withdrew the offer on July 13. After reportedly agreeing to terms on a two-year, $5.3 million deal on July 19, Ferrell backed out of his