The Welshman has made four changes to the side for their trip to Inverness with Munster hopeful JJ Hanrahan given the chance to impress at inside centre.
Michael Kearney returns in the second row while Martin Moore and Shane Buckley also make the starting lineup.
"We felt we have not been as effective in our defence as we would have hoped and have asked players to look at that and for a positive reaction," said Ruddock who coached Wales to their 2005 Grand Slam.
"If we can achieve that we will see an improvement."
15 - Michael Sherlock (Clontarf/Leinster)
14 - Tiernan O'Halloran (Galwegians/Connacht)
13 - Alex Kelly (UCD/Leinster)
12 - JJ Hanrahan (UL Bohemian/Munster)
11 - Andrew Boyle (UCD/Leinster)
10 - Patrick Jackson (Dungannon/Ulster)
9 - Blane McIlroy (Ballymena/Ulster)
1 - James Tracy (UCD/Leinster)
2 - Niall Annett (Belfast Harlequins/Ulster) (Captain)
3 - Martin Moore (Lansdowne/Leinster)
4 - Michael Kearney (Clontarf/Leinster)
5 - Daniel Qualter (Buccaneers/Connacht)
6 - Shane Buckley (Garryowen/Munster)
7 - Aaron Conneely (Corinthians/Connacht)
8 - Jordi Murphy (Lansdowne/Leinster)
16 - David Doyle (UCD/Leinster)
17 - Tadhg Furlong (Clontarf/Leinster)
18 - Iain Henderson (Queens/Ulster)
19 - Cathal O'Flaherty (Cork Constitution/Munster)
20 - Mark Dolan (Corinthians/Connacht)
21 - Gareth Quinn McDonogh (Shannon/Munster)
22 - Colm O'Shea (Old Belvedere/Leinster)