A crowd of 30,000 will witness the respective Guinness Premiership and Magners League champions go head-to-head for the second time in Pool 3 with a place in the European quarter-finals at stake.
McGeechan saw his 2005 Lions skipper Brian O'Driscoll run in two tries in Leinster's runaway, 41-11 victory in Dublin in Round 2 and must have been secretly pleased to have seen the Irish skipper in such good form.
And this weekend he will find his side confronted by another of the 2005 tourists, fit-again Godron D'Arcy.
But McGeechan says there will be no room for thoughts about the future on Saturday, only about what Wasps can achieve in trying to keep alive their European dreams.
"We need a good day. It's a big game with two top teams and it's a game we know we've got to win," he said.
"A lot of things happened the last time we met. We didn't play well and didn't cope well with things.
"We've got a lot of ground to make up. We are playing better now and we hope the injury count doesn't work against us.
"Twickenham is like our second home and we have done well there. It is a great place to be playing rugby and we are all looking forward to it.
"But I will only have a Wasps hat on. There will be a lot of answers Lions wise coming out of the Six Nations when we see players going head-to-head.
"That's the bit I will certainly get excited about. Although it will be mainly about the Six Nations, we have given ourselves four weeks after the championship to pick up on other players."