KEEPING Adelaide ruckman Sam Jacobs out of any sort of rhythm will be crucial to curbing the in-form big man's influence in Friday night's preliminary final at Adelaide Oval, Geelong's Zac Smith says. 

The in-form Jacobs has been a pivotal part of Adelaide's success this season, averaging a competition-high 39.7 hit-outs per contest (injured Fremantle big man Aaron Sandilands tops this, but played just 10 matches in 2017).

The match-up between Jacobs and Smith shapes as one of the most important on the field on Friday night, with both sides' gameplans so dependent on winning the engine room battle, with Adelaide ranked No.1 and Geelong ranked No.4 in the AFL for contested possessions. 

"Sam's ruck craft is really solid and it works against every type of ruckman," Smith told AFL.com.au.

"There's not one way to beat him. He's a big boy and he's got really good hands in close around the contest."

Smith said taking away Jacobs' ability to dictate terms with his positioning would be a high priority.

The two big men have squared off twice in games this season, with Smith emerging on top when the Cats beat the Crows by 22 points in round 11.

Jacobs was the clear victor when the teams met again in round 18, with the Crows winning the clearance battle 47-27 – the key factor in their 21-point victory. 

On that occasion, Smith felt like he was too easy to ruck against and played into Jacobs' hands. 

There were 38 ruck contests on the night, with Jacobs winning 21 hit-outs, including nine to advantage, and Smith recording just 12, and three to advantage. 

"I didn't use enough variety and that's probably what killed me that night," Smith said. 

At 202cm and 102kg, Jacobs uses his strength to advantage and he is adept at palming the ball down to an in-form midfield consisting of Matt and Brad Crouch and the returning Rory Sloane.

Jacobs' go-to move, at centre bounces, is to engage the opposition ruckman by encroaching on their side of the circle, once the ball is in the air, and then using his bulky frame to shift them off the line of the footy.

"I'll try to get him thinking about me more than the other way around," Smith said.

"If he uses that technique against me to come across the line, I could come around the other side of the circle and fully face off with him and just run and have a jump at it.

"If that wasn't working then I could come back around to the side he's on and wrestle him for prime position." 

Smith said limiting Jacobs' hit-outs to advantage was essential, while he is also planning to use his own strengths, such as his agility in general play, to advantage. 

For a player who stands 206cm, Smith has a unique skill set in that he is almost more proficient when the ball is on the deck than when it is in the air. 

The former Sun has averaged four clearances and 14.8 disposals per game in 2017, and showed against Sydney in last week's semi-final a real ability to manoeuvre his way through congestion and distribute to running players going by. 

"It all starts with being switched on from the get go," Smith said. 

"Usually it means my ruckwork is really good and then that allows me to follow up and make tackles or win clearances and just be involved in the play. 

"I've also got to identify times where I can push forward, but not overdo it. 

"I thought I did that really well last week and when I can go forward and snag a goal it not only lifts the team, but me personally as well." 

Smith said he would relish his duel with Jacobs, knowing that it will be a significant determinant in Friday night's result.

"You always want to play against the best and on one of the biggest stages it would be great to get one up on him (Jacobs) and help lead the team into the Grand Final next week," Smith said. 

Smith vs Jacobs (round 11, 2017)

72 ruck contests

Jacobs: 37 hitouts / nine to advantage / 15 disposals / five contested possessions

Smith: 29 hitouts / 11 to advantage / 13 disposals / five contested possessions

Smith vs Jacobs (round 18, 2017)

38 ruck contests

Jacobs 21 hitouts / nine to advantage / 11 disposals / four contested possessions

Smith 12 hitouts / three to advantage / 13 disposals / eight contested possessions

2017 – comparison

* stats provided by Champion Data