We are now less than four weeks away from the greatest National Hunt horse racing meeting on the planet. On Tuesday, March 14, the famous Cheltenham roar will be heard for miles as the opening day of the Festival gets underway – but plenty of punters will already have one eye focused on Cheltenham Gold Cup day.

In 2017, Sizing John cruised home to claim the coveted accolade under a superb ride from Robbie Power. Formerly aimed at shorter Grade One races, Sizing John always had potential and trainer Jessica Harrington never gave up on him. Having made the switch from two miles, he started to fulfil that potential and it wasn't a huge surprise to see him parading around the winner's enclosure.

But that was then and this is now. Sizing John will be back to defend his title but his recent form isn't fantastic. Will the champion respond at this year's Festival or are we destined to see a new Gold Cup winner? Only time will tell. Here are a few of the leading contenders in most betting markets ahead of the Cheltenham showpiece:

Sizing John
Be wary of Sizing John – he has the talent but is he fully fit? Regarded as one of the most versatile horses in the business, Sizing John was finally rewarded with Grade One glory after playing second fiddle to Willie Mullins's stable star Douvan for most of his career.

Far from a cert to replicate last season's winning performance, Sizing John has drifted in the antepost betting markets. The eight-year-old, versatile and tough on all types of ground, will be right in the mix on his best form but it is hard to back him with too much faith after that run at Leopardstown.

Coney Island
A month or so ago, Coney Island was valued at well over 16/1 in the betting. Now, he is as short as 10/1. Due to both a lack of viable competition and his own form against rivals, the seven-year-old has been backed considerably by ante-post punters.

He gave weight to the well-fancied Adrian Du Pont at Ascot in December but showed no remorse, winning by nine lengths. That result sent shockwaves across the racing world – Coney Island IS a serious contender. Oh, and he defeated More Of That, sixth in last year's Gold Cup, by 25 lengths on that day too.

Edwulf
Some racing experts believed that Edwulf would never compete again after his horror injury at Cheltenham last year, but the tough thoroughbred bounced back to claim a shock scalp in the Leopardstown Gold Cup at the start of February.

Edwulf was 50/1 on that day and that result got punters thinking. What if connections follow the natural route and send him to the Cheltenham Gold Cup? He will need to be lucky but luck is one thing that this particular racehorse has plenty of. Write him off at your peril - Edwulf could feature prominently.

Definitly Red
Handed top weight for the 2018 Grand National, the Gold Cup is now a viable option for Definitly Red. Plenty of racing fans have hinted at the potential U-turn and it may be wise to take advantage of favourable odds now. When at Timeform.com, readers can check the latest tips and offers ahead of the Festival.

Winner of January's Cotswold Chase at Cheltenham, Definitly Red looked right at home on the hallowed Prestbury Park turf and punters will be keeping a close eye on his progress in the coming weeks. He was beaten eight lengths into second by Blaklion less than two years ago and he should be right in the mix.

Native River
Labelled as the Gold Cup's forgotten horse less than two weeks ago, Native River sent out a statement of intent with a 12-length drubbing of Cloudy Dream at Newbury. Colin Tizzard was overjoyed at that triumph and he will be confident of going close – even with stable star Thistlecrack ruled out of the race. Highlights of that triumph are available in the video below.

Native River has the pedigree, he has the class and he has the stamina to compete with all of his rivals. He has been backed into 11/2 after that Newbury demolition, and it is easy to see why. If conditions suit, Native River could be the one to beat.

Killultagh Vic
A faller when Edwulf won the Leopardstown Gold Cup, Killultagh Vic should not be ruled out just yet. According to reports, he has been getting through some stellar work at home and it wouldn't be a huge surprise to see the Mullins horse prevail. Djakadam has had his chance – it is time for Killultagh Vic to fly the flag for the Mullins camp.

Prior to that run last time out, Killultagh Vic had won five races in a row, winning on soft, good and heavy ground. His versatility could prove useful come Gold Cup day - you certainly wouldn't bet against him featuring near the front at the business end of the race.

Our Duke
Another Harrington-trained star set for a Gold Cup push, Our Duke has the potential to go far. Capable of serving it up or holding back with a late effort, he won the 2017 Irish Grand National and another performance like that could be enough to secure another huge win for the stable.

He has won five of his 11 runs over fences to date and Robbie Power's decision on whether to stick with Sizing John or opt for Our Duke could be telling. Expect plenty of money for the latter if the 2017 winning jockey decides to go down this route.

Might Bite
Whatever you think of Might Bite's quirks, you have to respect this horse's stamina, speed and desire. Nicky Henderson has played down his overzealous nature on more than one occasion and punters have piled on to make Might Bite the clear ante-post favourite with most highstreet bookmakers.

Now priced at around 3/1, Might Bite has the recent form to stake a serious claim for Gold Cup glory. He won the King George VI Chase at Kempton Park on Boxing Day and Henderson believes that he will take all the beating come Friday, March 16 - and Henderson's word should be good enough for most.