It was 2012, and the quick-thinking midfielder was part of a string of Western Jets try-out games, hoping to do enough to be picked in Vic Metro's 50-man under-16s squad.
He had played for Victoria at under-12 and 15 level, and was desperate for another go in the national carnival. He played a couple of solid games but, while recovering from the broken bone, wasn't himself.
"I was hoping they'd pick me because they knew what I could do, instead of what I did," Ellis told AFL.com.au.
When they didn't, Ellis made sure he wasn't overlooked again.
"At that stage I was kind of in between with my footy and I had a think about it. I thought if I really want this I've got to work hard, and I did that," he said. "I find I've become a more resilient player now."
Ellis didn't make that cut, but he sits now as one of the better midfielders of this year's draft pool.
He's a player who has more to him than immediately meets the eye: in close he gets out of trouble with no trouble, he's not super fast but makes others look off the pace, and he seems ahead of the game, able to sum things up quickly and make the right decision. Importantly, he's trusted with the ball.
The skilful left-footer also enters an uncertain and nervy period of his football life with a broader view of the delicate position of being a draft hopeful. Of how it can go the way you want it to, or the other.
Ellis' football pathway has been closely linked with that of his older brothers, twins Brent and Mitch. That started in the backyard at home in Keilor, where they'd muck around, have a kick and a "bit of a wrestle".
It continued at their local club, where every second year Corey would play as a bottom-ager in the same team as Brent and Mitch, who are 15 months older.
In all four of those seasons the trio shared, they won the premiership. "I'm really grateful they've been around and I've been able to do those things with them," Ellis said.
Even that toe injury was a backyard incident when one of the twins (Corey can't remember who) stood on it by accident during a kick-to-kick.
So when Corey started training with the Western Jets' under-18 squad last year, and Mitch and Brent were already part of the team, he was comforted by their presence.
"I was really nervous and they'd be there to talk me though things, or help me out if I needed anything," he said.
His brothers, though, were going through their own challenges.
Brent had recovered from a knee reconstruction, but was struggling with the injuries that invariably follow, like hamstring complaints and shin splints. And Mitch couldn't break into the team consistently.
Neither was drafted, and after short stints with the Jets over summer and early this year as 19-year-olds, they returned to play locally at Keilor.
"Brent's knee injury was a bit surreal. It happened just landing from a marking contest and put him out for a year, and it makes you think you're very lucky to keep playing every week," Corey, 17, said.
"He's always been very positive about it all and has always tried to get back on the track.
"And Mitch, he's worked hard, he just hasn't got the rewards yet. He wasn't very lucky last year and unfortunate not to get seen by many, and that was disappointing for him.
"It just made me think about it all, and made me more committed, really. You don't get many chances, so when you get them you've got to take them."
Ellis emerged last year as a prospect, and has taken strides again this season. A nicely-sized on-baller at 186cm and 76kg, he can also be used across half-back and set up the play, like he did for Vic Metro in its first game of the NAB AFL Under-18 Championships two weeks ago.
He's been named there again for Saturday's clash with Western Australia, but is just as comfortable in the thick of the action.
"I love going through the midfield and I feel there I can use what I've got a bit better. But I don't mind half-back and running down and getting a few touches up the field," he said. "I've been fairly consistent this year and that's what I want to be."
The Jets have noted that, and have been buoyed by Ellis' development since a breakout game in 2013. Shane Sexton, the Jets region manager, knows how much he wants it.
"He's a pretty quiet kid, but quietly determined that he's going to get this done, and in a really successful way," Sexton said.
Meanwhile, the cycle at the Ellis household has continued.
The youngest of the four brothers, 13-year-old Nathan, has shown some talent, and the Jets will watch his footy progress over the next few years. So too will Corey, who will look out for Nathan just as Mitch and Brent did for him.
"We're a very close family so I'll go to Nathan's local footy some days and he'll come to mine whenever I'm playing," Ellis said.
"I think he's really taking something out of it too, like the professionalism side of things. He's just enjoying his footy, and he's starting to play better as well."