However, when fellow defenders Alex Rance and Luke McGuane were ruled out due to suspension in round 3, Grimes was called to take a key defensive role in the Richmond AFL side.

[14][26] Grimes spent part of the 2014/15 pre-season looking for a mental edge, reading extensively about mindfulness in competitive sport and serving as the catalyst for the introduction of a meditation program which when fully implemented two years later would become a key component of the club's success.

[40] He played a key role in the club's round 2 win over Collingwood, blanketing small forward opponent Alex Fasolo and keeping him goalless.

[41] Grimes was one of the club's best in round 5 too, recording an equal team-high seven tackles along with six intercepts and eight one percenters and earning himself two votes in the Coaches Association's Player of the Year award.

[14] His defensive work was strong though, earning particular praise for a goal-saving effort in round 4 that helped keep the Brisbane Lions to a club-record low score for any match against Richmond.

[61][62][63] Grimes followed that up with a season-best eight marks in Richmond's two-point loss to the GWS Giants that also saw him earn a vote in the Coaches Association award.

[65][66] In round 22 he recorded a match-high 16 one percenters and earned particular praise from Richmond head coach Damien Hardwick who labelled Grimes "an incredible player".

[67] At the end of the home and away season he was named in the 40-man squad for that year's All-Australian team and was nominated for the AFL Players Association's Most Courageous award.

[71] Following the conclusion of the 2018 finals series, Grimes was named by the Herald Sun's chief football writer Mark Robinson as the league's 9th best defender and the 45th best player overall during the 2018 season.

[77] Grimes immediately returned to training after surgery to realign the nose, wearing a protective face mask for more than a month while the injury continued to heal.

[80][81][14] Prior to the match, Grimes had been labelled by Fox Footy commentator Nick Riewoldt as "one of the best lockdown defenders in the competition" and highlighted as one of the league's most irreplaceable players.

[88] When he returned in round 4, AFL Media named Grimes a key candidate to captain the side in the absence of all three members of Richmond's leadership group, though he would eventually be passed over for the role in favour of veteran Shane Edwards.

[89] He led in another way, taking six marks in the final quarter in a best-on-ground performance that earned him his first three Brownlow Medal votes and that senior coach Damien Hardwick said "won the match for (Richmond)".

[100][101] In round 18, Grimes earned two coaches votes for a performance in a win over Port Adelaide that also saw him named to AFL Media's Team of the Week.

[108] During a match against West Coast in round 22, Grimes left the field with an ankle injury after landing awkwardly in a marking contest.

[110][111][112][113][114] Grimes concluded the regular season ranked 10th in the league for one percenters and 12th for intercepts, earning selection in The Age and the Herald Suns teams of the year.

[118][119] After nine straight wins to finish the home and away season, Grimes was set for another contest directly opposed to Charlie Cameron in a qualifying final against the Brisbane Lions at The Gabba.

[120][121] He produced a "dominant performance" to restrict Cameron to a single goal, helping Richmond win through to a home preliminary final against Geelong.

[138][139][140] Grimes then contributed five marks in round 1's win over Carlton in a match played under extraordinary conditions, the first of what had been announced would be a shortened 17-round season imposed on the league as a result of the rapid progression of the coronavirus pandemic into Australia.

[145][146] Within three days of the round 1 win however, the AFL Commission suspended the season for an indefinite period after multiple states enforced quarantine conditions on their borders.

[150][151][14] In early July, Grimes traveled with the club when all Victorian sides were relocated to the Gold Coast in response to a virus outbreak in Melbourne.

[152][153] He was among Richmond's best players in a round 7 win over North Melbourne two weeks into that stay, attracting six coaches award votes for a performance that included game highs in marks (nine) and one-percenters (nine).

[158][159][160] In the second quarter of round 14's win over West Coast, Grimes suffered a minor hamstring injury that resulted in him sitting out the remainder of the match.

[169][170] Grimes was below his best in the club's qualifying final loss to the Brisbane Lions, but was solid with a five mark performance in a semi-final victory over St Kilda one week later.

[173] He became a three-time premiership player in that 31-point grand final victory, playing a lockdown defensive role and keeping opposition small forward Gary Rohan goalless.

[186][187] Grimes proved instrumental in the victory, recording an equal game-high eight intercepts and performing a goal-line save to negate a potentially match-winning Giants shot at goal in the final minute of the match.

[15] In August 2020, Grimes was subjected to online abuse and harassment after he allegedly staged for a free kick in the round 13 Dreamtime in Darwin match.

[158][199] The day after the game, Grimes posted screenshots of abusive messages to his Instagram account demonstrating death threats received over the previous night.

[200] Victoria Police subsequently launched an investigation into the messages, resulting in charges being laid on two separate individuals within one week.

[201][202] The former charge will be heard in August 2021 and the later man avoided conviction at the Ringwood Magistrates Court in December 2020, on the condition he write a letter of genuine apology to Grimes, donate $1000 to The Alannah and Madeline Foundation and accepted a six-month good behaviour bond.