BRISBANE needs Harris Andrews to find his best form for Saturday night's semi-final against the Western Bulldogs.

Andrews, an All-Australian in 2019 and 2020 before missing the squad of 40 this year, was well below his best against Melbourne last weekend.

Matched up against Ben Brown, he looked out of sorts, struggling to match Brown's running up the ground and back into space.

From the opening bounce, Brown charged from centre half forward towards the middle of the ground, and when Melbourne won the clearance, he wheeled around and sprinted forward, leaving Andrews in his wake and crumbing the game's first goal.

Of equal concern was Andrews' timing. Known for his thunderous spoiling, the 202cm Lions' full-back was battling to get purchase on the footy and 'clear the area' when he tried to put his fist through the ball.

Why this stood out so much, was how rare it has been in his decorated 135-game career.

He was a late withdrawal from the crucial round 23 clash against West Coast, citing a tight hamstring.

The club denies it was an issue that hindered him against Melbourne, and although he doesn't have the smoothest running gait at the best of times, it was clear something was bothering him.

Perhaps it was a slight lack of confidence in his body or just picking the pace of the game up again after missing his only match of the year.

It's been slightly more of a mixed bag in 2021 than Lions fans are used to.

The good has far, far – did I say far? – outweighed the struggles, though.

Numbers alone show Andrews could be considered unlucky to miss that AFL Therabody All Australian squad of 40.

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He has been involved in more one-on-one defensive contests (122) than any player in the AFL, losing just 20.5 per cent of them.

The figure compares favourably with the key defenders that beat him into the AA team. Steven May (20.9 per cent losses) was around his mark, Aliir Aliir (17.2) one of the best in the competition, and Jake Lever (27) a touch worse, although his real strength lies elsewhere.

Jacob Weitering, who made the squad of 40, lost 20.8 per cent of his one-on-ones.

Prior to 2019 Andrews was known for his pure defensive prowess. He was a 'spoil first' guy that was hard to beat with his extensive reach, good speed and discipline to stop his opponent.

However, he knew his game had to evolve. On the eve of the 2019 season, Andrews told AFL.com.au the greatest point of improvement in his game was to incorporate more intercept marking.

"We saw in the (2018) Grand Final with Jeremy McGovern coming across and taking marks and winning he ball back for his team the value that bought, that's something I need to do to keep evolving my game," he said.

"There's going to be times when I make the wrong decision, maybe sometimes I should spoil and sometimes I should mark, but I'll try and limit those errors as much as I can."

The change in mindset worked almost instantly – and he rarely made the wrong decision.

That goes for this year as well. Andrews was ranked second behind Lever for intercept marks and overall intercept possessions – which coupled with his frugal defensive loss rate in one-on-ones, is a lethal combination.

Andrews has taken a couple of losses this season, though. Harry McKay kicked six goals on him early in the year, while Max King manhandled him with a three-goal quarter that set-up a St Kilda victory later in the season.

Andrews is Brisbane's defensive lynchpin and needs to be at his best against Aaron Naughton this weekend, a man that has posed some difficult questions in their handful of match-ups.

Just how much leeway Andrews gives his opponent in the search to employ his intercepting game will be fascinating viewing.