Altior and Douvan, both of whom have yet to race this season, lead 30 entries for the Betway Queen Mother Champion Chase at the Cheltenham Festival.
Nicky Henderson announced last season's leading two-mile novice Altior had undergone a wind operation in November but is working towards the March 14 event.
Willie Mullins initially said Douvan was out for the season in December, only to put him back in the mix for this race earlier this month.
Both trainers have more than one string to their respective bows, though, with Henderson having also entered Top Notch.
Mullins has nine entries to pick from, including last year's Ryanair Chase winner Un De Sceaux, who is also entered in that race again, Min and Yorkhill.
Paul Nicholls' Politologue has emerged as a major player for the two-mile crown after winning his first three starts this term, including the Tingle Creek Chase, and he could be joined by San Benedeto.
Politologue is owned by John Hales, whose colours were carried to victory in this race by One Man in 1998 and Azertyuiop in 2004.
He said: "Politologue is an improving young horse.
"We are getting him ready for the Game Spirit at Newbury on February 10, and then, all being well, he will go on to Cheltenham for the Betway Queen Mother Champion Chase.
"He has shown this season that he is a true two-miler, and not a two-and-a-half-miler. He has the cruising speed and tremendous jumping ability.
"The Tingle Creek meant a lot because it was a fabulous performance. His jumping was superb - quick and accurate - and I thought he won the race well.
"I am sure the horse will put up a good performance at Cheltenham. Whether we are going to be a match for Altior remains to be seen, but it is a race to look forward to."
Last year's winner Special Tiara, trained by Henry de Bromhead, also features among 17 Irish entries, with five contenders hailing from Gordon Elliott's yard.
Fox Norton, Waiting Patiently, Charbel and Ar Mad are other familiar names in the mix.