Following last weekend's 19-13 win in Llanelli, Ben Marshall forms a back row combination with Jordi Murphy and in-form number 8 Leo Auva'a.
With Steven Sykes rested after the birth of his first child, a boy, this week, Lansdowne's Neilus Keogh will partner Mark Flanagan in the second row.
In the back-line John Cooney links up with Noel Reid at half-back and Fionn Carr comes into a lightning quick back-three alongside Andrew Conway and David Kearney.
Speaking ahead of Sunday's final pool match, Leinster 'A' head coach Colin McEntee said: "We're pleased with our progress so far this year but we have another big test against London Welsh on Sunday.
"We''l have to be sharp and we'll have to be accurate because they're a tough side with a lot of flair out wide.
"We're in a good position in our pool having beaten Esher and Melrose previously, and to grind out a win in the manner in which we did in awful first half conditions at Parc y Scarlets was pleasing.
"The application of the players has been really high again this week and I know they're looking forward to the challenge.
"After last Sunday's win over Llanelli it's important that we back up that effort with another big performance and try to round off this pre-Christmas block (of games) on a high."
* There will be free entry for Leinster Season Ticket holders on Sunday upon presentation of this year's membership card.
LEINSTER 'A' (v London Welsh): David Kearney; Andrew Conway, Brendan Macken, Colm O'Shea, Fionn Carr; Noel Reid, John Cooney; Jack McGrath (capt), Aaron Dundon, Jamie Hagan, Neilus Keogh, Mark Flanagan, Ben Marshall, Jordi Murphy, Leo Auva'a.
Replacements: Tom Sexton, Jack O'Connell, Jordan Coghlan, Conor Gilsenan, Luke McGrath, Cathal Marsh, Darren Hudson.