The Tigers entered Saturday's match at Optus Stadium with just 27 fit players to choose from because of a devastating 17-man injury list.
Things were looking even bleaker for the bottom-placed side when veteran Dion Prestia pinged his calf in the opening minutes of the game.
But in a match that featured 14 lead changes, it was Richmond who kept their cool when it mattered most to snap a 12-match losing and post their first win of the season, 15.9 (99) to 13.10 (88).
The key moment came with the Eagles clinging to a two-point lead with just five minutes remaining.
After Harley Reid gave away a high-tackle free kick, both he and Elliot Yeo started running back towards their defensive 50m.
But with Yeo not realising until too late that he was the player who had been ordered to stand the mark by the umpire, a 50m penalty was paid, allowing Steely Green to nail the close-range set shot.
West Coast's No.1 draft pick Willem Duursma made things interesting with a stunning goal on the run with 88 seconds remaining, but Seth Campbell sealed the drought-breaking win for Richmond with a clutch long-range strike.
Although Richmond (1-7) remain on bottom of the ladder, they were at least able to celebrate their first win since beating the Eagles in round 19 last year.
"I'm really proud of the group - we're dealing with a fair bit off the field with availability and things like that," Yze said.
"I mentioned post-game, this would be easily one of the best wins I've been involved in because of that.
"We're dealing with a lot with availability, but you wouldn't know it with our spirit and our energy."
West Coast slipped to 2-6, but it was a big improvement on last week's 101-point loss to St Kilda.
Eagles coach Andrew McQualter rued the 50m penalty paid against Yeo.
"It was a 50m by the rule," McQualter said.
"That's what the rule was there for, and our players need to know that if a free kick is paid, you can't run out of the area. It is what it is."
Noah Balta produced a Herculean display for Richmond on the way to 19 disposals, 20 hit-outs, four contested marks, five clearances and three goals, while Jonty Faull and Campbell also kicked three goals apiece.
Jack Ross (29 disposals, 11 clearances) and Kane McAuliffe (28 disposals) were also influential.
Tim Kelly led the Eagles with 30 disposals, seven clearances and a goal, while Reid had a hot first half on the way to 26 possessions, 10 clearances and two goals.
West Coast used the week to celebrate the 20-year anniversary of their 2006 flag, with members of that team forming a guard of honour as the Eagles ran through the banner.
There were nine lead changes and plenty of blunders in the first half, with the biggest gaffe belonging to Richmond second-gamer Sam Cumming when he pumped the ball 50m the wrong way.
West Coast kicked the opening three goals of the second quarter - including a two-bounce special on the run from Reid - to open up a 12-point buffer.
But some strong marking in attack from Faull and two goals in the final minute of the half to Balta ensured the Tigers went into the long break with a 10-point lead.
West Coast entered the halftime break having lost a whopping 19 consecutive quarters - a record low for the club - but it was the late fadeout in the final quarter that would have hurt the most.