Willie Mullins reports the eight-year-old to be lame, with a small stress fracture or ligament tear thought to be the problem.
Douvan was limited to just two starts last term, having suffered a pelvic injury when beaten into seventh in the 2017 Queen Mother Champion Chase at the Cheltenham Festival.
Mullins said: "He was lame the other morning when I pulled him out. I just sent him straight up to his usual vet. He informed me this morning that he is lame on his good leg. He has had trouble on his near fore previous, but he said he is actually sore on the other leg.
"There is nothing obvious that he can see on it, but it might be a little stress fracture or a ligament tear. Feeling it with his hand, he can't find out - so he is just going through all the usual tests.
"Obviously any time a good horse is lame it is a concern, but we will know more in a day or two when we have all the tests done. I hope it is something that will only keep him out for a few days."
Douvan is a six-time Grade One winner over fences, with all those victories coming over no further than two miles and a furlong. However, Mullins had been considering a switch up in distance - and that may still happen once Douvan has recovered.
The trainer added: "He is a bit like Footpad in that he can do that two-mile stuff, but I was probably going to extend him out this year. He was working away, and (onwer) Rich (Ricci) was over last week and was delighted with how he looked. We were delighted with what he was doing - and he looked fantastic, better than last year.
"We hope this is only a mild hiccup, rather than a problem."
