Ruddock forms a back row partnership with Leo Auva'a and Conor Gilsenan, while Lansdowne forward Neilus Keogh partners Mark Flanagan in the second row.
Fresh from his matchday involvement with the senior team last weekend in Montpellier, Jack McGrath joins Aaron Dundon and Jamie Hagan in the front row.
John Cooney links up with Noel Reid at half-back and Brendan Macken, a try scorer in the pool opener against Esher, starts again at centre alongside Colm O'Shea.
Andrew Conway and Darren Hudson will provide plenty of attacking threat alongside David Kearney in a young and exciting back-three combination.
* There is free entrance for Leinster Season Ticket holders into Saturday's game upon presentation of this year's membership card.
LEINSTER 'A' (v Melrose): David Kearney; Darren Hudson, Brendan Macken, Colm O'Shea, Andrew Conway; Noel Reid, John Cooney; Jack McGrath, Aaron Dundon, Jamie Hagan, Neilus Keogh, Mark Flanagan, Ciaran Ruddock (capt), Conor Gilsenan, Leo Auva'a.
Replacements: Jack O'Connell, Tom Sexton, Jordan Coghlan, Jack Conan, Luke McGrath, Cathal Marsh, Andrew Boyle.