Northampton Saints v Ospreys: Full team news for tonight's pre-season game at Franklin's Gardens, and how to watch it
Matavesi replaces James Fish at hooker and Ratuniyarawa comes in for Tom Wood, meaning Saints have two regular second row forwards to call upon this week.
The black, green and gold had a shortage at lock for their 40-21 win at Bedford Blues last Friday, and they were also low on numbers at hooker.
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Hide AdBut Matavesi comes in on this occasion, meaning Fish can be named among the replacements.
Ahsee Tuala will also make his first appearance of pre-season as he starts at full-back, while Connor Tupai will start at scrum-half for Saints, having lined up against them for Bedford last week.
Tom Litchfield was at centre when he started and scored against Bedford, but the youngster is on the wing this week.
George Furbank remains at fly-half, while Fraser Dingwall and Matt Proctor come in at 12 and 13 respectively.
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Hide AdPaul Hill replaces Ehren Painter at tighthead, while Alex Waller comes in for Danny Hobbs-Awoyemi at loosehead.
Saints start with a formidable back row as skipper Lewis Ludlam lines up alongside Teimana Harrison and summer signing Juarno Augustus.
Ospreys have plenty of talent in their travelling squad, with the likes of Rhys Webb and Gareth Anscombe set to pose a big threat.
But former Saints favourites Stephen Myler and George North will not be involved.
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Hide AdSaints will be streaming tonight's game live on SaintsTV for free.
Saints: Tuala; Litchfield, Proctor, Dingwall, Collins; Furbank, Tupai; Waller, Matavesi, Hill; Moon, Ratuniyarawa; Ludlam (c), Harrison, Augustus.
Replacements: Auterac, Hobbs-Awoyemi, Fish, Painter, Garside, Wood, Irvine, Mitchell, Grayson, Hutchinson, Hendy.