Johnson - who won the Heineken cup in 2001 and 2002 said: "Our quarter-final is going to be a huge test before we even contemplate the next round. We haven't beaten Leinster away from home since our first game in the tournament in 1996.
Johnson's experience in the tournament will stand him in good stead before the difficult trip to Dublin at the start of April. "In the knockout stage the games get bigger and bigger, although even the Pool matches are like mini international these days. They have that atmosphere and intensity about them."
And Johnson believes that his side has what it take to go all the way.
"Having scraped into the quarter-finals we have got the feeling that the luck is with us this season. With the possibility of a home draw in the semi-finals we have a real added incentive to get through.
"I know my brother, Martin, is looking to go out on a high and what better note to leave on than my winning the Heineken cup again. I certainly know he doesn't want to go out of this competition as a quarter-final loser."