Pat Sanderson is back for his first GP match as captain since the near-miss against Gloucester in October, while scrum-half Matt Powell anticipates his hundredth Premiership appearance and fly-half Shane Drahm starts the game just 14 points from the 1,000-point Premiership landmark.
"The spirit and confidence within the camp has been transformed," Brain says. "The guys are in a pretty buoyant mood."
Veteran prop Windo is expected to be fit for the Harlequins match on Wednesday, December 27, after recovering from a slight shoulder injury, while 23-year-old Quinnell has drawn praise from Brain for the hard work he's put in with director of sports medicine Bob Stewart in his recovery from a knee injury. He could be back for the Northampton match on New Year's Day. Both will be welcome returnees as Brain juggles his squad to cope with the unique demands of the festive programme.
"Every team's entering uncharted water," he says. "We fully understand why the extra fixture's there, so that we can assist the preparation of the national side for the World Cup.
"The team that recovers the best between matches will do the best. There's not a lot you can do in terms of physical preparation, just make sure the players are clear about game plans for each match and that they're adequately recovered.
"The ideal scenario is that no one player should start more than two games, but, obviously, there are circumstances that dictate that a player might have to start all three."
He knows Irish will provide a very stiff test of his revitalised team's progress.
"They've got an exceptional lineout, a lot of pace and power throughout the side and they've had a very, very good 2006," he says. "Our defence will have to go up a gear. It will be a very difficult match, but we're a lot more confident going into this game than any other this season."
Team: 01 Darren Morris, 02 Chris Fortey, 03 Chris Horsman, 04 Craig Gillies, 05 Phil Murphy, 06 Drew Hickey, 07 Pat Sanderson (c), 08 Kai Horstmann, 09 Matt Powell, 10 Shane Drahm, 11 Mark Tucker, 12 Thomas Lombard, 13 Dale Rasmussen, 14 Aisea Havili, 15 Thinus Delport
Replacements: 16 Tevita Taumoepeau, 17 Aleki Lutui, 18 Tim Collier, 19 Tom Harding, 20 Ryan Powell, 21 James Brown, 22 Marcel Garvey