"He gives me the feel of a real open-class horse," says Williamson.
"And I know he can trot a half (800m) in 56 seconds, which I doubt any of his rivals can do.
"But he needs clear air early. If he can get away and get into a smooth trot then I am sure he will be fine because he doesn't seem like he will gallop in the run.
"But he won't want to be pushing and shoving early because that isn't his go. I am sure he can win, though."
Williamson says Murcielargo easily beat stablemate Springbank Sam in a private workout last week, suggesting the latter will need his comeback outing in race three today.
Williamson also rates the chances of Jags Invasion in race 11.
"I think he has a bit of x-factor and he will end up in open class, too.
"I am not happy with his 20m handicap, to be honest, but I think he has most of them covered."
The one Williamson is worried about is Master Lavros, who has looked sharp at recent trials.