Pre-draft On January 18, 2017, it was reported that Foster and Alabama teammate
Jonathan Allen declined their invitations to play in the
2017 Senior Bowl. On February 13, 2017, it was revealed that Foster underwent surgery on his right shoulder to repair a torn rotator cuff. Foster was one of 19 collegiate linebackers to attend the
NFL Scouting Combine in
Indianapolis, Indiana, but was sent home after getting into a heated argument with a student hospital worker while receiving his medical examination at the combine. Foster objected to the way he was being treated and was sent home before being able to meet with team representatives from any NFL teams. During the combine, it was announced that Foster had failed a drug test. On March 8, 2017, Foster attended Alabama's
pro day and set scheduled private meetings with NFL teams to discuss the incident that took place at the combine. On April 20, 2017, it was revealed that Foster's urine sample was reported as dilute, which is treated like a positive test. At the conclusion of the pre-draft process, Foster was projected to be a first round pick by NFL draft experts and scouts. He was ranked as the top inside linebacker prospect in the draft by NFLDraftScout.com, was ranked the top linebacker by NFL analysts
Mike Mayock and
Gil Brandt, and was ranked the second best linebacker (behind
Temple's Haason Reddick) by
ESPN. {{NFL predraft
San Francisco 49ers 2017 The
San Francisco 49ers selected Foster in the first round (31st overall) of the
2017 NFL draft. He was the third inside linebacker, behind
Haason Reddick and
Jarrad Davis, and the fifth linebacker selected in 2017. Foster was also the first of two linebackers drafted by the 49ers in 2017, along with
Pita Taumoepenu. On June 9, 2017, the 49ers signed Foster to a four-year, $9.03 million contract with $6.87 million guaranteed and a
signing bonus of $4.71 million. He joined a revamped linebacker corp that consisted of
NaVorro Bowman,
Ahmad Brooks,
Elvis Dumervil, and
Malcolm Smith. Foster was slated to backup newly acquired free agent Malcolm Smith, but was named the starting right outside linebacker after Smith suffered a torn pectoral during
training camp. He made his professional regular season debut and first career start in the
San Francisco 49ers' season-opener against the
Carolina Panthers and recorded three solo tackles and deflected a pass during their 23-3 loss. He left the game after suffering an apparent ankle injury. He suffered the injury in the first quarter while pursuing
Christian McCaffrey and was inactive for the next five games (Weeks 2-6). Foster's first career tackle came on the first drive after he tackled McCaffrey on a seven-yard reception. He returned in Week 7 and was named the starting middle linebacker after the 49ers released the veteran NaVorro Bowman. Foster finished the 49ers' 40-10 loss to the
Dallas Cowboys with five combined tackles, but left in the third quarter after suffering a rib injury. On November 5, 2017, Foster recorded a season-high 14 combined tackles in the 20–10 loss to the
Arizona Cardinals. He finished his rookie season with 72 combined tackles (59 solo) and a pass deflection in ten games and ten starts. He was named to the PFWA All-Rookie Team.
2018 On July 3, 2018, Foster was suspended two games for violating the league's personal conduct policy, stemming from a weapons offense and a misdemeanor drug offense. Following another arrest for domestic violence on November 24, 2018, Foster was released by the 49ers. 49ers head coach
Kyle Shanahan stated that the decision was made as the arrest and all other previous issues made him "very hard to trust".
Washington Redskins / Football Team Foster was claimed off of
waivers by the
Washington Redskins on November 27, 2018. Regarding the decision to claim him, Redskins senior vice president of player personnel,
Doug Williams, stated that he and the rest of the team were fully aware of the allegations that led to his arrest, adding that Foster would have to go through the legal process and accept any other punishment, from the league or elsewhere, before he could ever play in a game for them. He added that the Redskins decided to take a chance on him after consulting with a number of his ex-Alabama teammates on the team, and hoped that being around them would provide him with the "best possible" environment to succeed on and off the field. He was then placed on the commissioner's exempt list by the league. Head coach
Jay Gruden further added that it was not guaranteed he would ever play for the team, saying that Foster had "a lot of work to do" before they would accept him playing for them. In April 2019, an internal NFL investigation found no evidence to support his suspension, with his reinstatement to the team's active roster. Instead, he was fined two game checks and put into an accountability plan developed in conjunction with the
NFLPA and the Redskins, which included counseling, a living arrangement, weekly meetings, and community service to help him avoid future incidents. During his first practice with the team in May 2019, Foster fell and suffered a
torn ACL and
LCL and was subsequently placed on
injured reserve. Still recovering from the injury, he was placed on the
physically unable to perform list on July 27, 2020, and activated on August 9, 2020, before being placed on injured reserve again on September 5, 2020. His contract with the team expired after the 2020 season. On April 8, 2022, the
Miami Dolphins hosted Foster on a workout. On July 31, Foster had another workout with the
Seattle Seahawks, but no deal was reached.
Pittsburgh Maulers On January 27, 2023, Foster was signed by the
Pittsburgh Maulers of the
United States Football League (USFL). In his first professional football action since 2018, Foster started all eight games for the Maulers, recording 53 tackles, three tackles for loss, one half-sack, one forced fumble, five pass deflections, and one interception. The Maulers folded when the
XFL and USFL merged to create the
United Football League (UFL).
Houston Roughnecks On January 5, 2024, Foster was selected by the
Houston Roughnecks during the
2024 UFL dispersal draft. In eight games played, Foster recorded 30 tackles, three tackles for loss, one half-sack, one forced fumble, one fumble recovery, three pass deflections, and one interception. He was placed on Injured reserve on May 24, 2024. Foster was waived by the Roughnecks on August 19.
Arlington Renegades On August 20, 2024, Foster was claimed off waivers by the
Arlington Renegades. ==Personal life==