"Selection was difficult as it's the first time we have had to narrow our focus a bit and determine a cut-off point for players. A number of selections were very tight which is positive," he said.
"The group is predominantly 'tried and proven', but with some newer faces as well. It's an opportunity to get to know the players as well as an opportunity to have a look ahead and start to get a little bit of organisation done for the GUINNESS Series.
There are a number of players such as Tommy O'Donnell, Michael Bent, Stuart Olding, Andrew Trimble, Craig Gilroy and Felix Jones that were not considered due to injury, but some of these players may well be involved in the autumn as they return to full fitness and resume playing."
Schmidt added: "There are also a few players who have not yet had many opportunities to make an impression and a few youngsters who have been impressive in the early rounds of the PRO12 that we've left to keep working with their provinces.
"There is no doubting the challenge that autumn presents but we're looking forward to get a little bit of a head start this weekend."
IRELAND Training Squad (September 22-23, Carton House):
Stephen Archer (Cork Constitution/Munster)
Rory Best (Banbridge/Ulster)
Isaac Boss (Terenure College/Leinster)
Tommy Bowe (Belfast Harlequins/Ulster)
James Coughlan (Dolphin/Munster)
Sean Cronin (St. Mary's College/Leinster)
Gordon D'Arcy (Lansdowne/Leinster)
Keith Earls (Young Munster/Munster)
Luke Fitzgerald (Blackrock College/Leinster)
Declan Fitzpatrick (Dungannon/Ulster)
Cian Healy (Clontarf/Leinster)
Jamie Heaslip (Dublin University/Leinster)
Iain Henderson (Ballynahinch/Ulster)