Barrass was drafted by West Coast with pick 43 of the
2013 national draft, their third selection. On arrival at the club he expressed interest in eventually filling a leadership position. He returned in April to play his first game for
East Perth reserves (West Coast's WAFL affiliate). Playing slightly over half the match, Barrass amassed 17 possessions. He played a further seven reserves games for the year. Gavin Bell, West Coast's Head of Development, was impressed with Barrass's performance and noted his marking and ball use as standouts. Teammate
Josh Hill likened him to fellow defender
Jeremy McGovern for his intercept marking and ability to "read" the play, a comparison later echoed by teammate
Mark LeCras. In July, coach
Adam Simpson said Barrass was ready to play at AFL level, but noted the
backline was "pretty settled" and it would be hard for the defender to claim a spot. After McGovern
hurt his left hamstring against , Barrass replaced him in the senior side against in round 17 of the
2015 AFL season. On debut, he recorded 15 disposals and five marks. Barrass played two more matches to end the year; round 18 versus and round 22 against . He retained his spot for the majority of the second half of the season, He polled one Brownlow vote for the performance. Barrass said he had been galvanised by his previous match against Adelaide in 2015, when he had been outplayed by their forwards. He went on to play in his first
AFL finals series, but only managed an elimination final after West Coast were knocked out by the . Barrass had eleven disposals and took six marks; Post-season, Barrass won West Coast's Rookie of the Year award. Ahead of the
2017 AFL season,
Fox Sports journalists Riley Beveridge and Ben Waterworth named Barrass 'the rising star' at West Coast and a 'lock' in their defence. He returned to pre-season training in improved condition after feeling 'pretty fat' near the conclusion of the 2016 season. Barrass signed a contract extension prior to the
2017 JLT Community Series, tying him to West Coast until the end of 2019. but returned later in the week on a lighter program. After missing round 1, he played the next eight rounds of the season before being demoted to the WAFL after a poor performance against . Barrass returned against in round 13 and played the remaining games of the season, including the elimination and semi-finals. West Coast captain
Shannon Hurn was confident Barrass was not shaken by the experience. In June, during West Coast's round 12
bye, Barrass injured his back while using a
dustpan and missed the next six rounds. He returned for West Coast's finals campaign and played on
Mason Cox in the qualifying final. Cox did not score and was restricted to four kicks and two marks. In the
grand final, Barrass again played on Cox; the match-up was named one of three key match-ups for the grand final by
Terry Wallace prior to the game. Barrass outplayed Cox to half-time, restricting him to just one possession. However, Cox improved in the second half and finished with seven marks and two goals, while Barrass recorded ten marks and 17 disposals. Barrass signed a contract extension until the end of 2022 after the grand final. He was ranked as 'elite' (in the top ten percent of defenders) by Champion Data ahead of the
2019 AFL season. Barrass kicked the first goal of his AFL career in the first round of the 2022 season, his 100th game. Following the
2024 AFL season, Barrass requested a trade to Hawthorn. He was officially traded on 16 October, the last day of trade period. ==Statistics==