Ellis played a vital role in Hawthorn's 2008 flag campaign before a raft of injuries - including a serious calf tear - threatened to prematurely end his career.
Labelled injury-riddled and a risk, Ellis knew it was time to seek out a new home after managing just two games at the Hawks last year.
With nothing to lose, West Coast decided to take the punt on Ellis, who as an unrestricted free agent could move to the club of his choice.
Ellis spent the summer getting his body right, and showcased his array of talent in the Eagles' 84-point pre-season win over Fremantle on Tuesday.
The 25-year-old racked up 21 possessions through the midfield and across half-back before being subbed off midway through the third quarter.
Simpson, who spent four years as an assistant at Hawthorn before landing the top job at West Coast, knows the injury risks with Ellis will be forever present.
"He finds a way to get hurt," Simpson said half-jokingly.
But the rookie coach also knows the damage Ellis can inflict on opposition sides.
"It's the reason why we got him over," Simpson said.
"He's a No.3 draft pick, he's got good composure, he's talented, and he's got great character.
"We just need to get that body right."
Fremantle were second-rate in the 2.20.10 (148) to 0.10.4 (64) loss to the Eagles despite featuring 17 players who appeared in last year's grand final.
The Dockers' late start to the pre-season has put them behind the eight-ball, but the club is confident they can make up ground over the coming weeks.
New recruits Colin Sylvia (five possessions) and Scott Gumbleton (six possessions, two goals) were barely sighted against the Eagles.
Tagger Ryan Crowley and forward Chris Mayne are set to return for next Wednesday's clash with the Bulldogs at Etihad Stadium, but Hayden Ballantyne is in doubt with a leg injury.
West Coast utility Patrick McGinnity faces a nervous wait after dishing out a high bump on Danyle Pearce, while Docker David Mundy may also have a case to answer after flattening Mitch Brown.