However, they welcome back England internationals Alex Corbisiero, David Paice and Jonathan Joseph and Exiles' director of rugby Brian Smith reckons their return will be a timely boost.
"We had a lot of international players coming back and the challenge was to get them back into our system very quickly," said Smith.
"We needed to get them back into the groove."
London Irish have lost only once in their last 13 home games in the Amlin Challenge Cup but Gloucester have won their two meetings against London Irish in this tournament, one of them in the 2006 Amlin Challenge Cup final in 2006 (36-34).
However, Gloucester have won their last three away games in the competition so they know what it takes to win on the road.