A winner of five of his six starts over fences as a novice, the seven-year-old made a superb return to action over just two miles in the Fortria Chase at Navan last month and was back up to two and a half miles for the John Durkan Memorial Chase at Punchestown.
Flemenstar appeared to face his toughest task to date in tackling the previously unbeaten chaser Sir Des Champs, but he produced a foot-perfect round of jumping under Andrew Lynch to beat his fellow Cheltenham Gold Cup hope with plenty to spare.
Casey said: “There’s not a bother on him this morning. He didn’t have that hard a race really.
“I was a bit worried last week as he seemed very quiet and he was the same at the races yesterday, but maybe he’s just growing up.”
Casey is now looking forward to seeing his pride and joy test his powers over three miles for the first time under Rules in the Lexus Chase at Leopardstown on December 28.
The long-term target is Gold Cup, where his stamina will be tested even more severely over the extended three and a quarter miles of Prestbury Park turf.
“We have another big day coming up at Christmas. That will be his first run over three miles and it will tell us a lot more,” said the trainer.
“I don’t think he’ll have any trouble getting the trip there and as Mick Fitzgerald (former jockey) said, only time will tell how he gets on over the last couple of fences in the Gold Cup. Let’s just hope we get there.
“I don’t think he was fully ready for yesterday and I think he can improve between now and Christmas, but then he’ll probably need to. We’ll get his next race out of the way before we look any further.
“The good thing about him is the ground doesn’t make any difference, but obviously I wouldn’t like to run him on very firm ground.
“I never thought I’d have a horse like this and you have to give credit to the owner, as he could have sold him 10 times in the summer.
“If he’d sold him he wouldn’t still be with me, but he always said he wasn’t going to sell and I’m very happy he didn’t!”
Paddy Power have installed Flemenstar as the 2-1 favourite for the Lexus, with Hennessy Gold Cup winner Bobs Worth quoted at 9-4 with a run.
Lexus Chase, Paddy Power bet: 2-1 Flemenstar, 9-4 Bobs Worth (with a run), 100-30 Sir Des Champs, 9-2 Tidal Bay, 6-1 Sizing Europe (with a run), 7-1 First Lieutenant, Hidden Cyclone, 10-1 Quel Esprit, 12-1 Cristal Bonus, Pandorama, 14-1 Bog Warrior, Midnight Chase, Rubi Light, The Giant Bolster, Weapon’s Amnesty, 16 China Rock, 20-1 bar.