And with Leinster having got themselves back on track in the race for a play-off spot with a 6-0 success away to Glasgow Warriors, Boss insists his side have no intention of taking Zebre lightly.
He said: "The [Glasgow] win was the crucial thing for us. When the rain came in the second half a few of the backs were having to do jumping jacks to stay warm.
"It was a relief when the final whistle went. It could have gone both ways. It's effectively a seven or eight-point win.
"We have to keep the momentum going. We have been looking at the Zebre pretty closely. They haven't got their win yet but they've been unlucky in the last couple of weeks.
"They have been scoring some good tries as well and it's maybe one or two kicks for them. We don't want it to happen against us and we are back at the RDS so looking forward to that."
For the arrival of the Italians Joe Schmidt has made ten changes to the team which won in Scotstoun with Jonny Sexton among those to return at fly-half.
There will be home debuts for Michael Bent and Andrew Goodman as the European champions look to cement their place in the top four.
Gajan has also made eight changes from the team that went down at home to the Blues with several Italian internationals returning to the side.
Mauro Bergamasco, Quintin Geldenhuys and Carlo Festuccia all come into the pack while Matteo Pratichetti starts in the centres alongside skipper Gonzalo Garcia.
And Gajan called on his side to play with no fear away to Leinster, saying: "The poor attitude cost us the chance of a victory and the indiscipline and dropped balls allowed Cardiff to take advantage.
"The last three games have been better for the fans, this Sunday less so, but we need to rediscover that aggressive defence, our discipline and the right attitude that we showed in Munster and against the Scarlets.
"We've got nothing to lose against the European champions, but we have to be at our best and show what we can do."
At RDS Dublin, 6pm. Referee: Andrew McMenenmy (SRU, 16th competition game)
Assistant Referees: Stuart Gafikin, R Kerr (both IRFU)
Citing Commissioner: Tom McCormack (IRFU)
TMO: Alan Rogan (IRFU)
Live on RTE SPORT