The Exiles come into the game on the back of a comfortable 70-14 victory against Rovigo, although two tries conceded from lineout mauls have given the Aviva Premiership outfit cause for concern.
"We've got to stop the drive," Parr told reporters. "Up until last week it wasn't really something that was a concern. But you don't want to let it become a problem.
"We've been out [on the training pitch] trying to put it right, stamping it out now. We know what we are supposed to do in that position, but maybe we didn't do what we were supposed to do."
London Irish currently top the Pool One standings.