The changes in laws have meant a change in emphasis in the contact zone and the tackler has been given more opportunity to poach possession. It is one of the major reasons the Springboks have selected the Cheetahs 'fetcher' Heinrich Brussow.
The 22-year-old Brussow caused the Lions no end of problems in their 26-24 win over in Bloemfontein and his part in forcing 19 turn overs earned him a surprise call up from outside the Springbok squad. It means Heaslip and his back row colleagues, Munster's David Wallace and Croft, will be looking to make life difficult for him.
"We've got to go out there and win the battles - the contact zone and the collisions. If we win enough of them we will win the game," said Heaslip.
"The tackler has more leeway with what he can do and what he can get away with these days. In times gone past you didn't have to target the tackler much.
"But if their guy is on the ball, poaching it, you have to get him off it straight away. It means being aggressive at ruck time and being more accurate.
"When we are in defence we've got to get on the ball, tagging it and holding onto it to try to get the turn over or penalty. You have to target guys and get them off the ball."
As for Croft, he has had to change the pattern of his game in South Africa to concentrate on the harder graft up front demanded by the Lions coaches and game plan.
"With Leicester I tend to play a more expansive role in my position, but here it is more about the close quarter stuff. I'm enjoying that role," said Croft.
"I've always been a fully paid up member of the back row club, even though I've appeared in the second row for Leicester and England. Now I guess everyone will see I'm a back row forward.
"As a No 6 you need a No 7 who can shift off the back of the line-out and David Wallace can certainly do that. He has got great ball skills and is a good runner."