Dean Elgar believes South Africa have exposed weaknesses in the England side that the tourists can continue to exploit for the remainder of the Test series.
The Proteas are heavy favourites to tie up the four-match rubber at one apiece after setting England a huge target of 474 with two days of the second Test at Trent Bridge remaining.
Opener Elgar was the first of three batsmen, along with Hashim Amla and captain Faf du Plessis, to score a half century as South Africa made their hosts pay for conceding a 130-run deficit in the first innings.
The declaration arrived late on Sunday after the tourists reached 343-9, with Alastair Cook and Keaton Jennings forced to survive a menacing burst from Morne Morkel and Vernon Philander before the close.
With six full sessions to see out having been dismissed in 51.5 overs first time around, Elgar does not rate England's prospects of escaping without defeat particularly highly.
"According to the stats, it shouldn't happen," he told reporters, acknowledging that a successful run chase from England would comfortably represent a world record.
"The wicket is getting better but the odd ball is squatting a bit. It will be hard work for us to get 10 wickets but our bowlers are looking forward to it.
"We don't want an easy Test victory – it has to be hard work to win a Test.
"We have opened up a few cracks in their side and will be brilliant for us in the future in this series. I'm not surprised by the swing since [the 211-run defeat in the] Lord's Test.
"We've been playing brilliant cricket for two or three years as one of the best teams in the world."
Moeen Ali helped himself to four wickets as South Africa hit out during the evening session and the all-rounder believes much of England's hopes of keeping a series lead for the third Test at The Oval rest upon Cook.
The former captain overturned an lbw dismissal on review first ball from Morkel before he and Jennings edged nervously to 1-0 at stumps.
"We have got some very good batters who are capable of doing it," Moeen said of an innings where significant scores for either Jennings or Gary Ballance would be timely with regards to their long-term prospects of remaining in England's under-scrutiny top three.
"Cookie, when he gets in, is hard to get out and hopefully we will see that. We need a good foundation to bat six sessions.
"The top three can be very solid and bat time, then we have Joe Root in good form. But we will have a chat before play."
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