The Northampton Saints hooker was among the contenders to be named permanent skipper of the side when Lancaster first took temporary charge of England prior to the Six Nations but he was overlooked in favour of the Harlequins flanker.
Hartley was in impressive form during that tournament yet his campaign ended on a sour note when he was banned for eight weeks for biting the finger of Lions blindside Stephen Ferris in the win over Ireland.
The suspension brought back memories of a 26-week punishment for gouging back in April 2007 - a ban that led him to miss out on potential selection for the 2007 World Cup in France.
But Lancaster insists the New Zealand-born front rower is far from a liability as England go looking for victory in Port Elizabeth having seen the three-match series go the Springboks' way last weekend.
"Dylan has always been part of the leadership group, he's driven training, he's the first-choice in his position and is respected by the players," said Lancaster.
"In the changing room before the game you hear lots of voices. You have the captain's voice but I can guarantee you Dylan's voice is close behind, encouraging, shouting, motivating.
"He has been a key part of our leadership group and I know he will step up to the task on Saturday.
"I think it will add five per cent on Hartley this weekend, definitely."