The star eight-year-old is hot favourite for the two-mile championship, but has developed lameness in a leg.
Trainer Nicky Henderson, pictured, said he will have a more definitive idea of whether or not he runs at Cheltenham this morning.
The Seven Barrows handler said in a statement posted on his Twitter account: “Altior was unfortunately lame this morning in his near-fore leg and we have located some pus in the frog [of his foot]).
“He was still able to exercise in the water treadmill this morning, which he regularly does anyway, and a poultice will now be applied and left on overnight to draw out the pus. The foot will also be ‘tubbed’ [stood in salt water] at regular intervals and the shoe will hopefully be replaced first thing tomorrow morning. Both our vet and farrier are working very hard and are more than hopeful that he will even be able to canter tomorrow and therefore confident he will be clear to race on Wednesday. Obviously we will monitor the situation and keep everybody up to date with his progress, but there will nothing more to say until tomorrow morning.”
Altior is unbeaten in seven starts over fences and is due to face Irish ace Douvan, trained by Willie Mullins, in the showpiece event on day two of the big meeting.
Henderson’s ace has missed most of the season after undergoing wind surgery in November but made a most accomplished return to action in the Game Spirit Chase at Newbury last month.
Meanwhile, connections of Footpad feel that it will take a good horse to lower his colours in the Racing Post Arkle Challenge Trophy Novices’ Chase today.
Having produced three near-faultless displays since being sent chasing, the Willie Mullins-trained six-year-old, who finished fourth in last year’s Champion Hurdle, is expected to prove tough to beat at Cheltenham in his quest for a hat-trick of Grade One victories so far this season.
Assistant trainer Patrick Mullins said: “It should be a fabulous race and with Saint Calvados there should be a lot of pace.
“Our horse handles the soft ground and stays further than two miles and, touch wood, looks a very natural jumper. He is in great form at home and will be very hard to beat. ”
Patrick Mullins is also confident Getabird can win the Sky Bet Supreme Novices’ Hurdle in today’s opener for his father, Willie, especially as the six-year-old is expected to be suited by the testing conditions.
Patrick Mullins said: “I think the rain is definitely in his favour as he handles the soft ground and he stays further than two miles.
“He has travelled over fine and has had a good preparation. Obviously he has got to improve from his current performances, but he is more than capable of doing it.
“ He is a different type to a lot of our previous runners in the race.”