The striker has suffered from a back problem since the fifth round win against Everton but although he hasn't featured since then, coach Pat Holland hopes he'll be fit enough to make the bench at Vicarage Road.
"Simon's struggled with his back since Everton but I'm still hoping to get him on the bench," reported Pat.
"He's got ability and if we need to change things, his receiving skills are good and it might give us something different."
Other than that, Pat says we're full out for the tie. "Touch wood, we look alright," he added, before revealing that four schoolboys are likely to make the trip around the M25.
"We gave Archibald Troy his full debut on Saturday and I'm pleased for him, he'll come into the squad on Thursday," he said.
"We'll have four schoolboys involved, Archibald, Radwan Hamed, Jamie Davis and David Button. That's smashing for us and in terms of development, I'm really pleased at the moment. All the schoolboys that have come in have done well.
"Watford are a big side, they've got a game plan, they work hard for each other and I've been impressed with that.
"We have to match them but we have to be clever as well. We have the individual players to open them up with the pace of Andy Barcham and Jacques Maghoma and Phil Ifil comes back in the side. We have attacking options but we have to match them for discipline."
Simon Dawkins is the only doubt for tonight's FA Youth Cup quarter-final at Watford.