Dixon, a 21-year-old centre with only a handful of substitute appearances behind him, scored a hat-trick - his first tries for the club.
"His performance was exceptional for someone with so little experience," said his coach, John Kear. "I'd be a lot more confident about him in a semi-final than I was 24 hours ago, and he will come into contention."
Hull could need Dixon, because they finished this relatively comfortable victory with three players - Kirk Yeaman, Chris Chester, and Richard Swain - all off the field injured.
"We don't know how serious they are, but we will be putting out a strong team," said Kear after seeing his side go back into third in the SuperLeague.
There was never much doubt about the outcome; the way Widnes repeatedly squandered first-half possession saw to that. Adam Hughes's lost ball paved the way for Dixon's first try; Mick Cassidy's mistake set up Richard Horne; and a brilliant back-handed pass from the impressive Danny Brough provided Dixon with his second.
Hughes and Shane Millard kept Widnes in touch, and Gray Viane's try after the interval brought them back to within six points.
That was simply the signal for Hull to step up the pace though. Tim Holmes's fumble saw Stephen Kearney go over, and Graeme Horne then joined his elder brother on the scoresheet.
Dixon completed his treble from Brough's break before Gareth Carvell crossed.
Widnes at least finished strongly with tries from Viane and Daniel Frame; but their position now looks completely hopeless. With six games to play, they are five points behind Salford, and apparently doomed.
"I was happy with the effort from the players, and that's all I can ask for," said the coach, Frank Endacott. "At least we'll go down fighting if we are going down."
Widnes: Holmes; Emelio, Whittle, Hughes, Viane; Myler, Jules O'Neill; O'Connor, Millard, Julian O'Neill, Cassidy, Frame, Finnigan. Substitutes used: Whitaker, Smith, Mills, Fa'alogo.
Hull: Tony; Saxton, Dixon, Yeaman, Raynor; R Horne, Brough; Dowes, Swain, Carvell, Chester, Kearney, Whiting. Substitutes used: Thackray, Higgins, G Horne, McNicholas.
Referee: R Laughton (Barnsley).Reuse content