Running forward midfielder Jamie Cripps is seen as the guru of the West Coast mosquito fleet, and he’ll need to draw on every drop of his leadership against Geelong on Friday night to nurture his hurting small forwards through the Willie Rioli anti-doping shock.

The Eagles were rocked on Wednesday night when they were informed Rioli had returned an adverse analytical finding for urine substitution in a routine ASADA test.

Rioli faces a ban of up to four years – an outcome that could potentially end what seemed set to be a glittering AFL career.

The timing could not be worse, with the Eagles facing a tough road trip to the MCG in the semi-final against a Geelong side that is desperate not to go out of the AFL finals without a win.

Cripps has played an important mentoring role for Rioli and Liam Ryan, helping develop the talented indigenous pair into two of the most exciting small forwards in the game.

The Eagles need to shut down Patrick Dangerfield and Gary Ablett. Photo: Getty

Ryan and Rioli highlighted their importance to the side with star displays in last week’s 55-point elimination final demolition of Essendon. Ryan booted three goals in another flashy performance.

Rioli, who will miss the rest of the finals series after being provisionally suspended, finished with one goal and two score assists from 15 disposals.

Ryan and Rioli are close friends, and it remains to be seen how much the drama will rock Ryan ahead of Friday night’s semi-final against Geelong at the MCG.

The guidance of Cripps and indigenous leader Lewis Jetta is set to prove crucial in helping ensure the devastation doesn’t reach epic proportions.

Speaking a week before Rioli’s provisional ban was handed down, Cripps expressed his awe at watching Rioli and Ryan in action, and his pride at being able to help them achieve their goals.

“It’s awesome to learn a few things off them, and awesome to try to help them out,” Cripps said. “Being the older one of the small forwards, I try to show leadership to them. I’ve enjoyed playing with them.

“It’s exciting, because you don’t know what they’re going to do half the time. It’s unpredictable. It’s good to watch them. I’m glad they’re on my team.”

Rioli had to lose a staggering 16kg just to get his chance on an AFL list, and he fulfilled a boyhood dream when he became a premiership player last year.

The 24-year-old’s story was an inspiration for others, and he is one of the most popular personalities at West Coast. His honesty and genuine care for others have shone through during his time at the Eagles, but his career is now at the crossroads.

Rioli spoke recently of the importance Cripps has had on both his and Ryan’s AFL career.

“The reason we’re playing good footy is because Crippa’s been helping us a lot off the field, putting us in the right spaces and showing us how to run,” Rioli said at the time.

We’re just learning from him. I couldn’t ask for a better mentor. He’s always there when I need him.”

Cripps was diagnosed with type 1 diabetes just before the 2010 national draft. He kept the diagnosis a secret until the Saints snared him with pick No.24.

Cripps was traded to West Coast two years later, and he has steadily improved to the point where he is now among the elite small forwards in the competition.

“When I got here he was still pretty young and raw,” Eagles coach Adam Simpson said. “Everything he’s got to now is just through hard work.”

Willie Rioli at a West Coast Eagles media event in Perth on Wednesday, eight days after the routine ASADA test on August 20. Photo: AAP

From Geelong’s point of view, defender Tom Stewart believes his team can nullify Ryan and West Coast’s potent forward line.

Stewart said Ryan posed a huge threat, but he backed the Cats’ group of defensive “misfits” to shut him down.

“In terms of small forwards, they’re very, very classy, they’re silk, they use the ball exceptionally well and their pressure’s elite so we’ve got to keep a close check on them,” he told reporters on Thursday.

Mark Blicavs looks poised to return to defence to take on Kennedy or Darling, with Harry Taylor, Jake Kolodjashnij and Jack Henry also likely to be called upon to deal with West Coast’s talls.

West Coast will also face a big job shutting down Patrick Dangerfield, while also covering Gary Ablett.

Eagles coach Adam Simpson conceded he has some pondering to do about who to tag.

“That’s always the challenge when you play a team like Geelong – you take your pick,” Simpson said. “And sometimes you don’t tag because if you tag one, another one jumps up.”

First semi-final: Geelong v West Coast

MCG, 7.50pm

Head to head: Cats 25 Eagles 26 Drawn 1

Last clash: R6 – Cats 15.14 (104) bt Eagles 7.4 (46) at GMHBA Stadium

Last final: 2011 PF – Cats 17.15 (117) bt Eagles 10.9 (69) at the MCG

-with AAP