Faugheen won the Stan James Champion Hurdle at the 2015 Festival, but an injury sustained after winning the 2016 Irish Champion Hurdle ruled him out of defending his Cheltenham crown.
The nine-year-old has suffered a couple of minor problems this term, meaning his intended comeback was delayed until the Irish Champion Hurdle last month.
However, another issue saw him pulled out of the race 24 hours before the event and while Mullins initially thought Faugheen had a muscle problem, the setback has proved more serious.
“We had hoped Faugheen had just tweaked a muscle, but we’ve had it checked out and it’s a stress fracture,” said Mullins.
Min also missed an intended outing in the Irish Arkle at the end of last month and Mullins has confirmed the Grade One winner will also be an absentee in the Cotswolds next month. He added: “Min has a bruise. Hopefully both will still make the track this season.
“It’s a real shame with Faugheen, we needed everything to go right and obviously it hasn’t. There are options at Fairyhouse and Punchestown for Min, hopefully he makes one of them, while we’ll try to get Faugheen ready for Punchestown.”
Meanwhile, Persian Steel can prove his 66-1 success last time out was no fluke by following up in the Betway Best Odds Guaranteed Plus Handicap at Newcastle this afternoon.
He had obviously been showing plenty at home before he even made his debut for Brian Ellison as he was sent off favourite for a bumper at Catterick last February.
Another bumper followed but he showed only a glimmer of hope before Ellison switched him to the Flat.
Not surprisingly he found a mile too sharp first time out, although he fared significantly better when upped to ten furlongs.
Sent off at 80-1, he was beaten less than eight lengths into fourth behind a David Simcock-trained winner now rated 76.
In hindsight he should never have been 66-1 over an extended mile and a half, but he was a clear-cut winner with the 81-rated Henry Croft back in fourth, conceding just 3lb.
An opening mark of 76 is fair enough on that basis and he is the least exposed runner in the field.