The changes have been made due to No. 8 Andy Powell and reserve flanker Stephen Ferris sustaining injury in training.
Davies said, "Munster backrow forward David Wallace has been selected as the replacement for Andy Powell, while Leinster No.8 Jamie Heaslip will take Stephen Ferris' place on the bench."
"Both players suffered injuries this week in training and unfortunately their recovery has been slower than anticipated. Andy sustained a hand injury while Stephen has a lower leg strain."
Team Doctor James Robson said, "After treatment and further assessment of the injuries the medical staff believe precaution is the sensible option considering we are at the start of the tour. On this advice Head Coach Ian McGeechan believed it was better for the two players and the squad that they not play in the first match today."
"Both players are undergoing recovery regimes with the medical staff and both players are expected to recover and play a role on tour.
"It is important to understand that the management of injuries and their treatment is not black and white. One minute an injury will respond to treatment, then its nature can change, necessitating a change in the treatment regime. That is why we are continually monitoring the players and any injuries," added Robson.
British & Irish Lions (v Royal XV)
Lee Byrne (Ospreys/Wales); Tommy Bowe (Ospreys/Ireland), Keith Earls (Munster/Ireland), Jamie Roberts (Cardiff Blues/Wales), Shane Williams (Ospreys/Wales; Ronan O'Gara(Munster/Ireland), Mike Blair (Edinburgh/Scotland); David Wallace (Munster/Ireland), Martyn Williams (Cardiff Blues/Wales), Joe Worsley (London Wasps/England), Paul O'Connell (Munster/Ireland, captain), Simon Shaw (London Wasps/England), Adam Jones (Ospreys/Wales), Matthew Rees (Scarlets/Wales), Andrew Sheridan (Sale Sharks/England).
Replacements: Lee Mears (Bath/England), Phil Vickery (London Wasps/England), Alun-Wyn Jones (Ospreys/Wales), Jamie Heaslip (Leinster/Ireland), Mike Phillips (Ospreys/Wales), Stephen Jones (Scarlets/Wales), Riki Flutey (London Wasps/England).