Sweeney crosses for try against former club Boxing Day 2008
Huw Evans PA
Dragons Coach Paul Turner confirms fly half Jason Tovey and lock Luke Charteris fail late fitness tests, but centre Ashley Smith returns.
Joe Bearman, Grant Webb, Aled Brew, Pat Palmer and Matthew Watkins are also out. Those injured Dragons players join lock Adam Jones and flanker Dan Lydiate - who are out for the season - plus Danny Lee on the sidelines.
James Arlidge starts at outside-half as Tovey has failed to recover from a knock sustained in last weekend's win over Edinburgh. Bearman is replaced in the back-row by Newport RFC captain Andrew Coombs.
"I'm really hoping it's going to be a high energy game with a lot of movement of the ball and two teams trying to take each other on," said Dragons backs coach Darren Edwards.
"They've got quality players that we will have to stop and to do that, we will have to be in their faces. We are developing a style of play and it is attack."
Newport Gwent Dragons: Martyn Thomas; Will Harries, Tom Riley, Ashley Smith, Richard Fussell; James Arlidge, Wayne Evans; Hugh Gustafson, Tom Willis (capt), Ben Castle, Rob Sidoli, Hoani MacDonald, Andrew Coombs, Gavin Thomas, Toby Faletau.
Replacements: Lloyd Burns, Nigel Hall, Lewis Evans, James Harris, Rhodri Gomer Davies, Adam Hughes, Alex Walker.
Cardiff Blues face a triple header against the Irish provinces on home soil in the Guinness PRO12 in the coming months - and you can join us at BT Sport Cardiff Arms Park with a special ticket offer available NOW!
Judgement Day IV, Welsh rugby's Guinness Pro12 double-header to be played out in Cardiff on Saturday 30th April, has sold out the Principality Stadium middle and lower tiers and is three months ahead of record sales figures hit last year.
Singapore will host the next stage of the #StayStrongForOws fundraising and awareness campaign next month - that will also see former Cardiff Blues and Wales star Owen Williams return to the city where his life changed forever.
Join Cardiff Blues for Wales' home matches in the 6 Nations with our fantastic hospitality packages at BT Sport Cardiff Arms Park - but act quickly to take your place with our Scotland packages now SOLD OUT!