Only six of Sunday's side were involved in Monday's unique contest – the Sharks won 41-39 on aggregate at the end of a game split into one half under union rules and a second under league laws – and coach Jim Mallinder was relieved that his squad didn't pick up any injuries.
"That was always a worry but several of our players were away training with England and Scotland and we took the decision to rest one or two of the others," he said.
Speaking of Sunday's visit to the Madejski Stadium, he said: "London Irish didn't start the season too well but they are on a roll with six wins from their last seven outings. They were a bit short of confidence when they visited Heywood Road earlier in the season but are playing particularly well now.
"They are a very well organised and physical team and they play very disciplined rugby. We are expecting a very hard game and our hopes of reaching the end of season play-offs could depend on how we perform on Sunday and the following weekend when we head south again to face NEC Harlequins.
"We finally found some form in our last European games and hopefully we can carry that forward. On a positive note it was difficult selecting the side because there is a lot of competition for places at present."
The Sharks: 15 Jason Robinson, 14 Mark Cueto, 13 Dan Harris, 12 Graeme Bond, 11 Steve Hanley, 10 Charlie Hodgson, 9 Bryan Redpath (captain), 8 Stu Pinkerton, 7 Alex Sanderson, 6 Peter Anglesea, 5 Dean Schofield, 4 Chris Jones, 3 Barry Stewart, 2 Andy Titterell, 1 Kevin Yates.Replacements: 16 Charl Marais, 17 Stuart Turner, 18 Iain Fullarton, 19 Phil Davies, 20 Jos Baxendell, 21 Vaughan Going, 22 Nick Walshe.
Kick-off: 15.00 GMT