The Nigel Twiston-Davies-trained 11-year-old has not been seen since pulling up in last year's Cheltenham Gold Cup, which was his first run since he won the Haydock race in 2010.
Naunton handler Twiston-Davies said: "He has been very good.
"I haven't had him back very long and it was a case of had he taken one wrong step then we wouldn't have got him to the Betfair.
"It's so difficult when you have got a horse that has had a leg (problem), but he is as fit as I can get him without having had a run.
"Everyone says is he as good as he was, but who can say?"
Trainer Nicky Henderson is hoping to set Simonsig on the path to the Arkle Chase at Newbury's Hennessy meeting after revealing the grey was a "little bit behind" schedule.
Beaten only by Fingal Bay under Rules and winner of the Neptune Investment Novices Hurdle at the Cheltenham Festival, the six-year-old is as short as 11/4 with some firms for the two-mile championship.
Henderson said: "Simonsig is a little bit behind. He had a splint which annoyed him for a couple of days. He won't run next weekend, but he might go to Newbury."
Henderson will saddle Burton Port in the Hennessy itself, although he is wary of the burden the 2010 runner-up, who will be joined by RSA winner Bobs Worth, must carry.
Outlining running plans, he said: "Burton Port hasn't quite come to himself yet and he has got a horrible task as top weight in the Hennessy.
"Bobs Worth will go for the Hennessy and Long Run will run next weekend at Haydock, with Finian's Rainbow and Oscar Whisky going to Ascot."