Western Australia opener Marcus Harris made the most of South Australia's butter fingers to put the Warriors in a strong position after day one of the Sheffield Shield clash at the WACA Ground.
Harris made 114 to lift the Warriors from a precarious 3-60 to a competitive 7-327, but the 20-year-old rode his luck along the way.
Michael Klinger was left to rue the one that got away after dropping Harris at first slip when the left-hander was on just six.
Then when Harris was on 51, wicketkeeper Tim Ludeman grassed a tough chance diving to his left.
The double reprieve came back to haunt the Redbacks, with Harris spending 276 minutes at the crease and cracking 19 boundaries to post the second century of his fledgling first-class career.
In March last year, Harris became the youngest player in Australian first-class cricket history to reach 150 when he made 157 against Queensland.
Harris was just 18 years and 227 days old at the time, and admitted he had struggled to string consistent performances together since then.
"It was a difficult year for me last year. I couldn't consolidate my spot," said Harris, who averaged 28.75 from 13 first-class hit-outs before this match.
"And I've had a frustrating start to this season.
"I've been hitting the ball quite well and I haven't been able to get past that 35-run sort of mark.
"So it's good to get a big score under my belt today and hopefully set up a good result for WA."
After winning the toss, WA were in all sorts of trouble at 3-60 following the cheap dismissals of Liam Davis (four), Sam Whiteman (14) and Marcus North (7).
Harris should have been added to that mix, but Klinger spilled a chest-high catch at first slip off the bowling of paceman Chadd Sayers.
It was a day to forget for Klinger, who also dropped North when the former Warriors skipper was on seven.
North failed to add to his tally before hitting out.
Harris wasn't as generous, but his day was finally brought to an end when he tickled a Jake Haberfield leg-side delivery through to the keeper.
All-rounder Mitch Marsh picked up where Harris left off in making an unbeaten 51, while Nathan Coulter-Nile (52 off 52 balls) and new Warriors skipper Adam Voges (47) also made handy scores.
The Warriors, who will announce Justin Langer as their new coach later this week, sit last on the Shield table following three outright losses, while South Australia have one win from four games.