THE TIMING of Willie Rioli's provisional suspension could hardly be worse for West Coast.

Already facing a mountain to climb to defend last year's premiership from fifth, the Eagles are reeling on the eve of a cut-throat semi-final against Geelong.

Somehow they have to overcome their shock, devastation for a much-loved teammate and the loss of one of their most talented players to keep their season alive.

It will be one of coach Adam Simpson's toughest tasks in six seasons at the helm.

At the eleventh hour, speedster Jack Petruccelle has flown to Melbourne and will play.

RIOLI DRUG TEST SHOCK Willie cops provisional ban

The 20-year-old must get his head around doing his job on the big MCG stage, five days after appearing in a WAFL final.

Petruccelle is capable and has kicked 20 goals from 19 games this year, but Rioli is irreplaceable.

The goalsneak's creativity, touch of class and ability to set up a teammate in a better position is magnified in the pressure of big games.

His dazzling opening against the Bombers helped set the tone last Thursday night.

Defying the odds as the first non-Victorian team to win the flag from outside the top four this century just got a whole lot tougher.

But beyond the immediate finals campaign, it's impossible not to hold fears for Rioli's career.

It is unclear exactly what happened under the adverse analytical finding of "urine substitution" during an ASADA test two days after the loss to Richmond on August 20.

The Eagles are still fact-finding, but his test produced something other than urine.

With a maximum four-year ban hanging over his head, Rioli was described as an emotional mess by football manager Craig Vozzo.

"He's very, very flat. The club and the staff are really worried about his wellbeing. He's not in a great space," Vozzo said.

For a player who worked so hard to earn his AFL opportunity, it is a shattering turn of events.

Rioli remarkably shed 16kg to be drafted as a 21-year-old via pick 52 in the 2016 NAB AFL Draft.

It hasn't been smooth sailing since, with his first season wiped out by hamstring issues, and the Tiwi Islands product has had weight battles during periods of rehabilitation.

But, along with Liam Ryan, he sparked West Coast's rejuvenated forward line last year and helped inspire the Eagles to a stunning premiership.

On Grand Final day, Rioli flukily kicked their desperately-needed first goal – his 28th for the season – amid Collingwood's onslaught.

Rioli celebrates his crucial goal in the Grand Final. Picture: AFL Photos

He was then among the four starters West Coast trusted for the most important centre bounce in club history after Dom Sheed's famous match-winner.

Along with a premiership medallion, he took home the club's Emerging Talent Award and finished 10th in the John Worsfold Medal last season.

Rioli's star continued to rise this year as he built his fitness and explored his midfield craft.

The sky has seemed the limit for one of the AFL's most watchable natural talents.

But even Vozzo found it difficult to say exactly what Rioli's future now holds with an investigation looming.

"I know he's a wonderful young man who we love and respect, and we're going to help him get through this as a football club," Vozzo said.

"Our players are very emotional, they love Willie, but we've got a pretty mature team.

"I'm confident they'll be able to package their feelings for a couple of hours and perform at their best (against Geelong).

"As a club, we've had a bad period in the past. We've worked really hard for 15 years to improve in a whole lot of ways.

"Very proud of our players and the standards they set off the field in the community and trying to be good people, and we'll continue to do that."