A physical Samoan out-fit caused England plenty of problems and the Sale giant is expecting another tough encounter against the Lions' last opponents.
"Census (Johnson) is a big lump who slams into you at the scrum and while the Springboks may not be that big, it will still be very tough," said Sheridan.
"They are always physical and confrontational. They won't have taken kindly to losing to Scotland and will be coming at us with everything.
"It would be a great achievement if we can finish the autumn series with three wins.
"Samoa caused us lots of problems at the break downs and I am sure we are going to have a lot of clean-out drills in training this week to improve our work in this area.
"I'm sure South Africa will look at what Samoa managed to achieve and we will have to tighten things up.
"It is important that we get the balance right in attack and we don't want to stifle the enthusiasm of our guys who want to take the game to the opposition but, at the same time, you need to get the fundamentals in place.
"We had some problems that needed to be sorted out and it was pleasing to come away with a good win against very physical opponents. I see the Samoans as the prototype for a rugby player because they are very powerful, skilful and agile."