Mark O'Connor has made a career out of doing things that not many others can do. 

Since joining Geelong as a category B rookie at the end of 2016, the Irishman has been nothing but reliable and quietly goes about his business, consistently playing whatever role the team requires. 

But while he potentially does not get the limelight that he so rightly deserves, O'Connor's journey on a path less frequently travelled has been nothing short of ground-breaking throughout his career with the Cats. 

Now set to play his 150th AFL game on Thursday night when Geelong do battle with Adelaide at GMHBA Stadium, O'Connor will reach a milestone that only five other Irishmen in V/AFL history have reached. 

GEELONG, AUSTRALIA - FEBRUARY 18: Mark O'Connor and Mark Blicavs of the Cats share a laugh during the Geelong Cats 2026 Official Team Photo Day at GMHBA Stadium on February 18, 2026 in Geelong, Australia. (Photo by Sarah Morton/AFL Photos)

Mark O'Connor's journey started as a rookie heading into the 2017 AFL season, not taking long to make an impression at the club and earning his AFL debut in Round 8 against Essendon. 

He would go on to play two games in his inaugural season with the Cats and a further five the following year, before solidifying his spot in Geelong's starting line-up in 2019. 

Across the journey he has been asked to play a plethora of roles, most notably making a name for himself in defence while able to play a lockdown or rebounding role with his skill and decision making. 

But O'Connor has also been deployed in the midfield at times and can utilise his bigger frame to impact stoppages, most notably collecting eight clearances in 2021 on Easter Monday against Hawthorn, which also doubled as his lone career Brownlow vote to date.

One of the most effective performances the Irishman has put together was in a negating role, doing a stellar job on the likes of Noah Anderson and Cam Rayner throughout last year. 

The crowning moment of O'Connor's AFL career so far came in 2022, when he featured in Geelong's premiership triumph over Sydney. 

Many will remember the Irishman's tone-setting chase down tackle in the opening quarter of the Grand Final, running down James Rowbottom in the corridor and stopping a threatening Swans attack which ultimately led to a Cats goal down the other end. 

Alongside fellow countryman Zach Tuohy, the pair became just the second and third Irish-born players to ever stand atop the premiership dais in the league's extensive history. 

From that moment onwards, O'Connor has continued to be an ultra consistent performer for the Cats and never takes a backward step. 

GEELONG, AUSTRALIA - AUGUST 08: Mark O’Connor (left) and Oliver Dempsey of the Cats celebrate during the 2025 AFL Round 22 match between the Geelong Cats and the Essendon Bombers at GMHBA Stadium on August 8, 2025 in Geelong, Australia. (Photo by Michael Willson/AFL Photos)

During the off-season, O'Connor returned home to Ireland and featured in another incredible achievement with his side, Dingle as they claimed their first All-Ireland Senior Club Football Championship. 

Played at Croke Park, Ireland's principal national stadium, O'Connor and his Dingle teammates prevailed in an extraordinary match, in what was described as a historic national championship victory.  

It primed the Irishman to return and attack Geelong's pre-season, hitting his straps as he heads into his 10th season with Geelong in 2026. 

O'Connor will reach his 150th AFL game this Thursday night, as Geelong prepares to take on Adelaide at GMHBA Stadium in Round 3.