Wales coach Warren Gatland said his England counterpart Steve Borthwick must be ready to counter the "dark arts" of South Africa's Director of Rugby Rassie Erasmus ahead of their World Cup semifinal on Saturday.
Gatland, whose side went out in the quarterfinals to Argentina last weekend, wrote in a column in the Daily Telegraph on Wednesday that England must match the defending champions both physically and mentally in Paris.
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At a press conference on Tuesday, Erasmus had answered a question about who he thought Borthwick would field by reading out a possible line-up and Gatland said that was an attempt to unsettle England.
"Rassie has already tried to gain a mental edge and sow seeds of doubt by naming what he thinks Borthwick's team will be for the semi-finals," wrote Gatland.
"To have any chance against the Springboks you must attempt not just to match them physically but also to be tactically smart and show no signs of mental weakness."
Gatland and Erasmus fell out during the 2021 British & Irish Lions tour of South Africa where Erasmus acted as a "water boy," running onto the field and passing on instructions while wearing a bib reserved for those who carry refreshments to the players.
This was later banned by World Rugby, with Gatland quipping: "If he is going to act as a water boy, at least he should have some water in his bottle".
Gatland also wrote he did not like South Africa's "win-at-all-costs attitude where the end justifies the means" and suggested England ask questions "about the number of head injury assessments (HIA) South Africa called for in their victory against France."
Two players went off to be checked by doctors at the insistence of Springboks coaches during the quarter-final win over the hosts on Sunday.
When asked on Tuesday whether he would ever use the HIA regulations to rotate players and give them some rest during the game, Erasmus answered with a curt "no."