HE HAS done a number on some of the best midfielders in the competition, but Geelong's Irish stopper Mark O'Connor has perhaps never faced a test quite like the one he will come up against on Friday night.

Against a Western Bulldogs midfield that ranks No.1 for clearance differential and No.2 for disposal and contested possession differential, O'Connor's new tagging role will be put to the test against one of the competition's elite onball brigades at GMHBA Stadium.

Having emerged as an important shut-down midfielder in Geelong's thrilling round two victory over Brisbane, O'Connor thwarted reigning Brownlow Medal winner Lachie Neale in a bullying display.

Champion Data notes that Neale had just eight disposals in 91 minutes directly matched with O'Connor, who himself had an impact offensively to win 15 touches of his own, as well as five clearances and seven tackles.

That performance set the scene for O'Connor's career-best season in his new midfield role, with the 57-game Cat – recruited from Gaelic side Kerry in October 2016 – quickly moving his attentions to some of the game's other elite midfielders.

Tom Mitchell was kept to 21 disposals in 94 minutes when directly paired with O'Connor, Clayton Oliver to 17 disposals in 72 minutes, Tim Kelly to 14 disposals in 70 minutes and Travis Boak to 22 disposals in 89 minutes.

MARK O'CONNOR'S 2021 TARGETS

It's important to note that O'Connor hasn't spent the entirety of games matched against his opposite number, making the comparisons with their 2021 averages slightly misleading in some cases.

But there can be no doubt as to the 24-year-old's impact in a role he was only asked to start playing earlier this season, highlighting the credentials that saw him quickly elevated into Geelong's leadership group in 2020.

In addition to blanketing some of the game's best midfielders, O'Connor has also won plenty of his own footy this year. His 26 disposals, eight clearances and eight tackles in an Easter Monday win over Hawthorn complemented his shutdown role on Mitchell.

But a hamstring injury sustained in the side's emphatic victory over West Coast kept him sidelined for six weeks, before he immediately renewed his newfound position in a narrow win over Port Adelaide last Thursday night.

One week on, he will turn his focus towards the Western Bulldogs and an in-form midfield group that will feature superstar Marcus Bontempelli and his supporting cast of Jack Macrae, Tom Liberatore, Lachie Hunter and Bailey Smith.

Who he goes to is another question, one that Geelong coach Chris Scott will undoubtedly have spent the week pondering and one that could swing the fortunes of the Cats on Friday night.

Bontempelli is the obvious candidate. The classy midfielder is clearly among the frontrunners for the Brownlow Medal after a season in which he is averaging close to 27 disposals, five clearances and five tackles per game, while kicking 17 goals from 12 matches.

But is he stoppable? And is Macrae, either? The latter is averaging 35.2 touches per game, leads the League in disposals, uncontested possessions and effective disposals, and is in the midst of a 24-match run where he's claimed 30 or more disposals in full length matches.

It perhaps makes Liberatore a prime candidate, especially given the success Melbourne enjoyed when James Harmes turned tagger for a one-off game and frustrated the clearance king earlier this year.

Liberatore, averaging 24.2 disposals and 8.5 clearances per match, is pivotal in the way the Western Bulldogs midfield group operates and has become the No.1 stoppage player in the competition this season.

But he was kept to just 16 disposals and four clearances against Melbourne – both clearly season-lows for the campaign – as Harmes inspired his Demons side to a stirring 28-point win.

"We need to think through it," Scott said on potential match-ups for O'Connor this week.

"Anyone could answer that question more generally by highlighting the quality of their players. They're all a little bit different and some clubs have put some work into their damaging users behind the ball like Bailey Dale and Caleb Daniel.

"Bontempelli might be the best player in the competition, Macrae is the leading disposal winner in the competition and Liberatore is one of the better contested and stoppage players.

"That's not even thinking about their players who are ahead of the ball, so we've still got a little bit of work to do to decide exactly which way we go. But if you focus your attention on one of them, the rest of them get you. We'll prioritise balance over anything."

Balance or not, O'Connor will still perform a crucial role on Friday night. Who he tags, and how limited their performance is as a result of the added attention, could be influential in the game's final outcome.