Richards played college football at the Stanford University, where he was a team captain and first-team All-Pac-12 Conference player during his final senior collegiate year with the Cardinal.

[2] He played for the West team under former Seattle Seahawks quarterback and Washington Redskins head coach Jim Zorn.

[4] On March 19, 2015, Richards opted to participate at Stanford's pro day, along with James Vaughters, Ty Montgomery, Andrus Peat, Lee Ward, A. J. Tarpley, Alex Carter, Henry Anderson, David Parry, and five others.

[7] At the conclusion of the pre-draft process, Richards projected to be a fifth to seventh round pick by the majority of NFL draft experts and analysts.

Many journalists and analysts speculated his selection by Patriots' head coach/general manager Bill Belichick was due to his solid performance in the three-cone drill, his intelligence, and high football acumen.

[16] Upon arriving at training camp, he competed with Nate Ebner, Tavon Wilson, Duron Harmon, and Brandon King for the role as a backup safety.

Head coach Bill Belichick named Richards the backup strong safety behind Chung to start the regular season.

He made his first career regular season tackle on Jaguars' running back Corey Grant and stopped him after an eight-yard reception in the first quarter.

On December 20, 2015, Richards earned his first career start and recorded three solo tackles and defended a pass in a 33–16 defeat over the Tennessee Titans.

He started at free safety after Devin McCourty was unable to play after sustaining an ankle injury the following week against the Houston Texans.

[19] The following week, he earned his second consecutive start at free safety and recorded a season-high seven combined tackles during their 26–20 loss at the New York Jets.

On January 26, 2016, he played in the first career playoff game as the Patriots defeated the Kansas City Chiefs 27–20 to advance to the AFC Championship.

[21][22] Richards entered training camp competing for a job as the backup safety against Ebner, Harmon, King, Brock Vereen, Vinnie Sunseri, and Cedric Thompson.

[28] During a Week 6 matchup against the Jets, Richards earned his second start of the season as a hybrid coverage linebacker and recorded three solo tackles in a 24–17 win for New England.

[37] In Week 17 against the Pittsburgh Steelers, Richards recovered a punt fumbled by punter Jordan Berry in the end zone for a touchdown during the 28–10 win.