IT IS high stakes for Fremantle as a top-four spot goes on the line against a struggling West Coast team that will be motivated by the prospect of damaging its rival's prospects.

Nathan Schmook breaks down the keys to Saturday night's Derby 59.  

How ruthless are the Dockers? 

With just six points separating Fremantle in fourth and Hawthorn in 11th, the Dockers are well aware that there is no room to slip up in games like this. The need to be ruthless was put on the agenda immediately after the Melbourne win and it can be interpreted as not taking the foot of the pedal for any periods within games. Consistency within matches is what will separate the top four teams from the rest in the final five rounds, and the Dockers have a golden opportunity to earn the double chance if they are ruthless during that period.

Which midfielder gets the Eagles' attention? 

While a hard tag is unlikely, there have been times that the Eagles have used Zane Trew to be accountable for an opposition gun during Jarrad Schofield's two games in charge. The difficulty is in deciding which Freo midfielder to put time into. Caleb Serong is the No.2 clearance player in the AFL and has lethal hands, Andrew Brayshaw ran riot with 41 disposals last week, and Hayden Young is punishing opponents in the front half and setting up more goals than any Docker. Managing the Dockers' dominant stoppage game is the first step, so Serong is probably the player to be most wary of. 

Will a Derby reignite the Eagles' midfield? 

The other side of the coin is a talented Eagles midfield that may just lift for this occasion. Elliot Yeo (26 disposals and six clearances) and Harley Reid (19, seven and three goals) were irrepressible in the round six Derby and shape as the Eagles' key to winning the return bout. Led by Reid, the Eagles put on five goals to one in the third quarter in round six to put the game out of reach, controlling clearances (12-7) and contested ball (38-18). It's a perfect place to start if they are going to win this one in what would be an even bigger upset. 

The ruck battle 

The difficulty the Eagles will face at stoppages is restricting the elite ruck work of Sean Darcy and the athletic assets of forward/ruck Luke Jackson, with Bailey and Jack Williams the players who will be set the task. Bailey Williams was effective when he targeted Melbourne big man Max Gawn in round 11 and made life difficult around the ground all day for the star Demon. He'll need to make it hard for Darcy to direct his taps and then hope he can get involved at ground level. Still, the ruck is arguably the area of the ground where the Dockers have the biggest advantage. 

Eagles' size versus Dockers' speed

The selection of Jack Darling came as somewhat of a surprise in a forward line that also includes tall trio Oscar Allen, Jake Waterman and Jack Williams. What he can provide, however, is tackling pressure after the Eagles failed to lay a forward 50 tackle last week. He'll need to, with Fremantle lining up with rebounding trio Jordan Clark, Brandon Walker and Corey Wagner and coming off a game which saw them launch plenty of late scores from their defensive half. Schofield was confident he had talls who could contribute at ground level. The challenge will be there for them.  

Eagles' size versus Dockers' youth 

The direct match-ups Allen, Waterman, Williams and Darling will confront will include returning key defender Josh Draper, who steps back in for injured skipper Alex Pearce. Draper has played 15 games and the Dockers have confidence in him to play his role in a likely battle with Allen or Waterman, particularly after an outstanding performance in round 16 against Sydney that included some match-winning moments. The advantage Fremantle will have is in Luke Ryan, who has consistently stepped up when a first-choice key defender is unavailable, not only to lock down on an opponent but to roll off and prevent isolated one-on-ones for his young teammates.

Milestone games

Another source of inspiration for the Eagles will be the milestone games of Tom Barrass (150) and Waterman (100). Both have been outstanding contributors through this season, with Waterman set to challenge for All-Australian honours and both expected to push for podium finishes in the best and fairest. Barrass, however, will enter the match amid uncertainty about his future at the club. The premiership star has three years remaining on his contract, but rivals are circling with longer term offers in an attempt to poach one of the game's best key defenders. 

The Purple Army 

West Coast's best games this season have been in front of a vocal home crowd that was re-energised by the emergence of Reid and the standout seasons of Yeo and Waterman. Indeed, all three of their wins have been in home games and are memorable for the electric atmosphere created by crowds that pushed well past 40,000. This Derby will be different as a predominantly purple crowd gets behind its team's top-four charge. The Dockers had won five straight derbies before the round six upset, and it's hard to picture a repeat of that result on Saturday night in a match the Dockers should win comfortably if they are the premiership contender they appear to be.