Philip Hobbs admits he is "stumped" by the disappointing performance of Defi Du Seuil at Ascot on Saturday.
The eight-year-old was sent off favourite for the two-mile-five-furlong Chanelle Pharma 1965 Chase, but failed to fire and trailed in 35 lengths behind impressive winner Lostintranslation.
Owned by JP McManus, Defi Du Seuil was having his first run since a wind operation and 301 days off the track.
Held up early by Tom O'Brien, Defi Du Seuil tagged on to the coat-tails of the leading trio after the ninth of the 17 fences, but was nudged along soon after and weakened after two out.
Yet Hobbs was making no excuses and said: "He was in good form after the race, back in the stable.
"So, I'm a bit stumped to be honest at this stage, but we will see how he is in the week.
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"We can't make any plans until we know what the issue was. The ground was fine - it was on the easy side of good - no excuses over that.
"He has run below par, that's for sure, but why? Only time will tell."
Sporting John back with a victory
Hobbs also revealed that high-class hurdler Sporting John could make his reappearance at Cheltenham next month.
Winner of the Grade One Virgin Bet Scilly Isles Novices' Chase at Sandown in January, the six-year-old subsequently failed to complete in two subsequent top-class chases at the Cheltenham and Aintree festivals, before making a successful return over hurdles in a Listed three-mile contest at Cheltenham's November fixture.
Though he holds an entry in the Cheltenham Gold Cup, Hobbs is keen to keep him over the smaller obstacles for the time being and the Citipost Handicap Hurdle on the Friday of Cheltenham's International meeting is pencilled in.
Hobbs said: "If the ground is suitable, Sporting John will be likely to run in a three-mile handicap hurdle at the next Cheltenham meeting. He is in good form."