England wicketkeeper Geraint Jones identified Jacques Kallis on Sunday as the primary reason for South Africa's recovery from one-down in the five-match series to 1-1 after last week's third Test.
Kallis has scored 448 runs with two centuries and has spent almost 22 hours at the crease.
"Kallis is a machine. From behind, the application he puts to every ball is phenomenal," Jones said.
"When you see Jacques just patting the ball back and not looking like getting out it is tough to keep the guys going.
"Someone like Brian Lara, with his flashing blade, offers you a chance and you feel at some point he may nick one. With Kallis it's different, he is so solid and you can see he just loves batting and batting.
"He holds them together because his team-mates see him and follow on from that. He values his wicket so highly. Early on he has shown that he can nick one and on a bouncier wicket, hopefully in Johannesburg, he could offer a chance.
"But at the moment he is tough to get out; he is playing the hook shot well and is generally keeping it on the ground. One or two have gone in the air and found gaps but maybe at the Wanderers he'll get unlucky. It's an area we'll have to examine."
England fans chanted "boring, boring Kallis" during his patient innings' of 149 and 66 at Newlands in the third Test. He responded by saying he would be happy to "bore England every time".
"Standing behind him is not so much boring as a war of attrition to get him out because he is so focused on the way he wants to play," Jones said.
"You think at times he might up the tempo a bit but he just carries on batting and leaving balls that you think he may play a cut shot or a big drive to, but he just leaves them to go through."
The fourth Test starts at the Wanderers in Johannesburg on Thursday.
