Prop Watts was surprisingly sold to Castleford in mid-March amid claims he had off-field issues so this weekend’s fixture was always pencilled in as one to watch.
Hull used some of their new-found salary cap to bring in ex-England loose forward Joe Westerman less than a fortnight ago after his surprise release from Toronto Wolfpack.
He was not expected to regain full fitness for a few weeks yet after a period of inactivity with the Canadian club but could make a shock return for Hull - where he played from 2011 to 2015 - on Saturday.
Westerman, who grew up with Featherstone-born Watts and played alongside him for four years at the Black and Whites, also started his career at hometown Castleford.
Radford said: "He's training really well.
"He's looked sharp this week, he's going to add to what we've got.
"I honestly don’t know which way to go with him - do we try push a little bit quicker?
“That’s results depending I’d imagine. (But) we've got selection tomorrow and anybody who is fit has got a chance at the minute."
Radford confirmed that stand-off Jordan Abdull is facing a lengthy lay-off after breaking a leg in last Saturday's 25-24 defeat by Catalans Dragons and his half-back partner Albert Kelly will miss the Castleford game after failing to recover from a hamstring injury sustained in Perpignan.
The unfortunate Abdull was due to play for partnership club Doncaster against Bradford last weekend and was drafted at short notice into Radford's squad for the trip to France after Marc Sneyd fell ill.
"It was a great opportunity for him, he was the next man up," Radford said.
"To leave the field like that is tough for him. It's tough for us as well.
"He'll have to have an MRI scan to see what ligament damage there is in there but I think he'll need a plate.
"It's going to be a long one. We'll have to see what the specialist says at the end of the op, hopefully we'll get a timescale from there.
"It's one of those seasons, we've had our spine on the field for two games and I haven't been able to pick the same 17 twice.
"Naturally you want your best players on the field, I understand you can't always have that, but we haven't had them on the field a great deal."
Radford confirmed that Sneyd will be back to face the Tigers, along with full-back Jamie Shaul, who missed the trip to Perpignan because of a family bereavement.
Meanwhile, Radford hinted that Kelly is set to become the first out-of-contract player to re-sign for the club.
"I think an announcement is due to be made," he said.