The horse put in a dashing front-running display to win the 4250m feature last year and is the early favourite for the race tomorrow.
The Big Opal signalled he was ready to defend his Koral crown with another bold front-running win in the McGregor Grant Steeplechase at Trentham on June 9.
Whanganui trainer Kevin Myers gave the 10yr-old a quiet time after that before tuning him up for the Grand National carnival with a run on the flat at Trentham late last month.
The Big Opal has the perfect opportunity to win a second Koral as his main rivals look vulnerable.
Upper Cut will shoot for his third consecutive win in the Grand National Steeplechase. Trainer Mark Oulaghan thinks his charge will need his Koral hit-out to peak for next weekend's feature.
Upper Cut ran a fair fourth in last year's Koral before his Grand National win.
Whether he can improve on that effort is questionable despite coming into this year's race with more racing behind him.
''He will probably need the run a bit on Saturday, but hopefully if he gets through that he will be pretty competitive in the National,'' Oulaghan said.
''We had him going a little bit earlier this year and he had a couple of flat runs and a hurdle race at the beginning of the season. Then we went a bit quiet with him. He just had a flat run the other day . . . [for third over 2100m at Trentham eight days ago].
Topweight Wise Men Say is in a similar position and is also expected to peak for the Grand National Steeplechase.
The star chaser needs to carry a massive 72.5kg in the Koral. That means he gives Upper Cut a 1kg advantage and The Big Opal a 3.5kg advantage.
Wise Men Say's part-owner, Mark Connors, whose son, Raymond, trains the horse at Whanganui, told NZ Racing Desk the Koral Steeplechase should help peak the horse for the Grand National.
''He's well and the weight makes it tough, but it should top him off for the Grand National.''
Prolific steeplechase winners Wise Men Say and Amanood Lad will race at Riccarton for the first time tomorrow.
The 14yr-old Amanood Lad signalled he was on his way back to his best with a solid third behind Wise Men Say in the Wellington Steeplechase on July 14.
Fellow Koral contender Chocolate Fish ran second.
