Under the charge of jockey Richard Johnson, the horse delivered Hobbs a memorable win at Prestbury Park, claiming the Festival's cross country race by a short head at 5-1 odds.
Hobbs - who has never won the National in 25 years of trying - is concerned that the ground at Aintree might not be good enough for his stable star.
But he remains among the 73 entries for the race, with 27 scratched at Tuesday's forfeit stage.
Johnson completed the course on Balthazar King last year but he came home a distant 15th of 17 finishers. Hobbs will also take Chance Du Roy - who won the Becher Chase at Aintree last December and finished second in the Topham Chase - to a course he clearly relishes.
"Balthazar King seems better than ever but he'd only run if the ground is no worse than good to soft," said Hobbs.
"He run below his best last year and a lot of our horses were not right at the time. Both our horses are good each-way chances."
As expected Irish champion trainer Willie Mullins has withdrawn Gold Cup runner-up On His Own from the big race to focus at the Punchestown Festival next month.
And the Ted Walsh trained Seabass - last year's favourite and third two years ago - won't race after a disappointing run at Down Royal on Monday.
Teaforthree, trained by Rebecca Curtis, remains the ante-post favourite after finishing eighth at last week's Gold Cup while Welsh National winners Monbeg Dude and Mountainous are also fancied.
The world-famous £1 million four and half mile handicap chase is expected to be oversubscribed - which means the lowest-rated horses will be balloted out closer to the off.
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