The Seven Barrows trainer felt the six-year-old was a bit fresh for his first run since winning the Cheltenham Gold Cup when beaten by Kauto Star in a memorable Betfair Chase at Haydock last Saturday.
Henderson expects Long Run to improve for the outing and is looking forward to a re-match in the Christmas cracker, in which Robert Waley-Cohen’s ace ended Kauto Star’s run of four successive King George victories last winter.
“I thought his jumping for the first circuit was better than it’s ever been. It was exemplary,” Henderson told At The Races. “The trouble was he was doing a little bit too much. By the time they got to the last after a circuit, he jumped upsides Kauto Star and just got racing there. That’s not what we normally do.
“He was just a bit fresh at that stage and his jumping was that good that he was getting up there.
“We then got locking horns with Kauto Star and then he made one mistake and it rattled him and got him and he then wasn’t going anywhere for a bit. Then he ended up jumping well up the straight again and ran on again.
“He’s done well because at the last coming out of the back straight, you think what has happened, he’s going to finish fourth or fifth. He’s got back, I’m not saying he’s got back to threaten him, but I just think he was doing a bit too much early on.
“He was just a bit fresh. At one point he and Kauto Star were taking each other on and Kauto won that battle comfortably.
“Kauto deservedly won the battle, but we’ve not lost the war. There is improvement to come, he will be like that first time.
“I think he’d done plenty of work. I don’t think he necessarily blew up. I just think there was a bit of rustiness about it and a few things to learn from it.
“Nothing changes our plan and we will head for Kempton and probably take him on again.
“We’ve just got to get him ready for Kempton and he will be.”
Henrietta Knight, meanwhile, has some trepidation about letting Somersby take on Kauto Star and Long Run in the King George.
The seven-year-old gelding ran an excellent race to chase home Master Minded in Saturday’s Amlin 1965 Chase at Ascot and is now set to step up to three miles for the first time.
Master Minded, four-time King George winner Kauto Star and last year’s victor Long Run are all in line for this season’s renewal.
“He’s come out of the race fine and he’s in good form. I was very pleased with how he ran on Saturday,” said Knight. If he hadn’t have got so close to the third-last, I think he might have finished a bit closer.
“He was probably in front a bit too soon, but he ran a good race.
“We look forward to stepping him up to three miles for the King George.
“I would be a bit anxious about taking on Kauto Star and Long Run, but the track suits Somersby and the step up in trip should help him.”