Cape Town - Head coach Rassie Erasmus says he has settled on around 80% of his Springbok squad for this year's World Cup in Japan.

There are just five Test matches remaining for the Boks before their World Cup opener against the All Blacks in Yokohama on September 21, but there are just four Tests left before Erasmus must select a squad of 31 Boks that will go in search of a third Webb Ellis Cup. 

A shortened Rugby Championship sees the Boks play Australia, New Zealand and Argentina over July and August, while there is also a one-off Test against Argentina the week after the Championship ends. 

It means that Erasmus has limited time left for experimentation, and he confirmed to media in Cape Town on Tuesday that the Boks would look to field their strongest possible side between now and the World Cup. 

The only possible window for change, Erasmus said, was likely to be that one-off Test against the Pumas at Loftus on August 17, but that would depend on the Boks' form.

"This year there is only one strategic goal and that's the World Cup," Erasmus said.

"The first thing is that we would love to win the Rugby Championship, so we will select teams that we feel can win the Rugby Championship.

"In that last Argentina game, it depends where we are. If we're on a roll then you won't want to change things but if we're not on a roll then you might do things differently to try return to winning ways.

"We definitely have the World Cup in our mind and I see ourselves picking our strongest possible side for the Rugby Championship."

Injuries, of course, can still change things and there have already been massive blows to the Bok cause with Lood de Jager and Warren Whiteley currently sidelined. 

If everyone stays fit, though, then Erasmus is unlikely to turn to players who were not heavily involved in the 2018 international season. 

"It's going to be tough for guys who have only played one or two Test matches to force their way in," he said.

"There would have to be injuries.

"I would say about 80% of the squad is pretty much settled, but as we saw with Lood and Warren, injuries happen.

"A guy can also just knock down the door totally, so maybe 70% or 80% we are settled on."