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.
Existing Season Ticket holders are advised that full details of all packages for the 2015/16 season have now been posted out to you and will arrive in the coming days - and that the deadline to renew your seat has now been extended!
Supporters are advised that Cardiff Blues will be holding a presentation on the field post match on Saturday afternoon to mark those players leaving the region, hand out caps and the end of season awards.
First team stars Cory Allen, Ellis Jenkins, Adam Jones and Kristian Dacey were among the special guests as Cardiff Blues held the Sphere Solutions Blues Tag Rugby Festival at BT Sport Cardiff Arms Park.
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.
Cardiff Blues will be celebrating St David's Day when the region faces Edinburgh Rugby at BT Sport Cardiff Arms Park on Sunday afternoon (kick-off 12.45pm) - with hundreds of children invited as part of our Regional Schools Day.