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.
Wales will host the opening games of the Singha Premiership Rugby 7s Series at the BT Sport Cardiff Arms Park as the four Welsh Pro teams go head-to-head in an exciting afternoon of summer derby rugby.
Can't get tickets for the Rugby World Cup? Well now you won't have to miss a second of the action alongside passionate fans as we are running two special events so you can watch the big games with Cardiff Blues and in the company of some Welsh rugby legends!
One of the most eagerly awaited events of the British motorsport calendar - the British FIM Speedway Grand Prix - will return to the Millennium Stadium on Saturday, July 4 - and at Cardiff Blues we've got FIVE PAIRS of tickets up for grabs!
The players at Cardiff Blues will be hoping to play with some true Gallic flair for the rest of the Guinness PRO12 season - after the region teamed up with a successful French bistrot in the Welsh capital.