Adam Simpson’s side suffered a serious blow during the pre-season as they lost reigning best-and-fairest winner Eric Mackenzie to a ruptured ACL in a recent NAB Challenge clash with Carlton.
And, the situation just worsened on Sunday when Xavier Ellis strained his hamstring in another preseason clash, this time against Port Adelaide.
The shift to defence may be just the change Rosa needs, after the midfielder has endured a rotten run with injuries over the last three seasons.
“I've spent this pre-season mainly down back, but that's more just been we've been unlucky with guys going down in the back line,” Rosa told the West Australian newspaper.
"I spent most of the weekend's game on (Justin) Westhoff, which was a good experience. I haven't really played tall back before.
"It was good to get a look at that. I don't mind playing back there. It's a good challenge.”
Mackenzie, for his part, has vowed to return a better player in 2016. And, on the injury himself, he initially felt it was hardly serious at all.
“I went to step to impact the contest. The next thing I know I was on the ground,” he told the Eagles website.
“I thought I got booted in the knee, I thought I’d be right to get up but I couldn’t straighten my leg.
“I knew something was wrong then.
“I thought it’d just go away, as I said I thought I just got booted in the knee, a bit of bone bruising and I’d be able to run off.”
“Because I managed to get up, and I started jogging off towards the end of it so I thought I’d be right to come back on.
“It’s only when the physios started doing the tests, I know what the ACL test is, they weren’t happy with the results so they took me down to the rooms.”