"Slow wicket, quick wicket - if a guy's bowling at 150km/h it's quick," said Morkel, the Proteas bowler who came closest to matching Johnson for pace in the first Test in Centurion.

"I don't think the wicket ... will play a big role if a guy's effective or not effective. He's bowling well, he's got his tail up at the moment, so it doesn't matter about the pace of the wicket."

Morkel also rejected the notion Johnson had been so dominant in the first Test, claiming a career-best 12-127, that it would have given the Proteas players "nightmares".

"Not really. I mean he's been bowling really well, and coming from the Ashes where he had so much success he's full of confidence. That's part of sport," Morkel said.

"For us, it's a great challenge to play against. I wouldn't say there's fear, it's just for us to really stick to our game plans and come up with game plans.

"In P.E. it will be slightly different to the Highveld [of Centurion]. More for us it's about fronting up and playing it. I know our top-six guys are seeing it as a nice challenge.

Both teams completed their first training session at St George's Park in Port Elizabeth on Tuesday, ahead of the start of the match on Thursday. Australia fast-bowler Peter Siddle said based on his appraisal of the pitch he was not expecting to encounter drastically different conditions to last week.

"It's still a bit thick and thatchy, the grass. It's been a bit windy and there's bit a bit of heat out there so it's probably going to dry out a little bit, and break up by the end of the Test," Siddle said. "I can't see it being a lot different to Centurion, really."

Australia looks set to field an unchanged team as it seek to build on its one-nil lead.

Shane Watson looks accomplished in the nets but took no part in the squad's rigorous warm-up activities, instead walking laps of the arena as he continued his recuperation from a calf injury suffered at the start of the month. On Tuesday, Watson took part in some jogging routines at the end of the session with strength and conditioning coach Damian Mednis, but is yet to resume bowling.

South Africa was forced to withdraw Ryan McLaren from its 15-man squad due to a bout of concussion that forced him into hospital on Sunday evening, caused by a hefty blow to his helmet from a Mitch Johnson bouncer that cut him on the fourth, and ultimately final, day of the first Test.

In selecting a replacement for McLaren, a bowling all-rounder, the Proteas will have to decide which discipline has a greater need for reinforcement in Port Elizabeth: batting or bowling.

The former would pave the way for Dean Elgar's inclusion, the latter would favour Wayne Parnell, a lively left-armer who with good pace and can achieve late swing.

Siddle expected Parnell, a 24-year-old whose only three Tests came at the start of 2010, would pip Elgar for the final spot.

"It's hard to tell. What we knew coming into the series was they were the two blokes they were looking at to replace [Jacques] Kallis in the line-up, so that's the way we look at it," he said.

"We were pretty lucky out there [at training]. A couple of the 'netties' [net bowlers] were left-handed so it gave the boys a bit to look at them.

"It's hard to tell whether they'll go with Parnell or with the extra batter, but I'd guess Parnell is going to be up there with that first chance."

Morkel reckoned selectors faced a "tricky" selection dilemma, declaring: "I'm just as excited as you guys to see what they come up with."

"Wayne [Parnell] has been bowling quickly this season, and also the left-armer is a nice option for us," said Morkel, who said selectors could promote Robin Peterson and Vernon Philander in the batting order rather than put Parnell, who has a first-class batting average of 22.34, in the number-seven slot McLaren held in the series-opener.

While 26-year-old Elgar thrived against Australia A in a series in South Africa last year, making 268 in one innings, his Test experience against Australia has been miserable. On his debut in Perth last season he fell for a pair to Johnson, while in the first Test he was the substitute fielder who dropped David Warner at fine-leg when the Australian was on 26. He went on to make 115.

Morkel was adamant Elgar, who scored an unbeaten 103 last season in Port Elizabeth against New Zealand, boasted a strong enough character to not be daunted by his as-yet poor record against Australia. He likened the left-hander's tenacity to that of a Staffordshire Terrier dog.

"Dean is like a Staffy. He's tough as nails. I'm sure if he gets the nod he'll be more than capable of doing the job," Morkel said.

While South Africa paceman Dale Steyn has been the world's best fast-bowler for must of the past five years he was comprehensively outplay in Centurion by Johnson, albeit coming off a limited preparation due to injury and a bout of gastro during the match. Clarke predicted an improved showing from the 30-year-old in Port Elizabeth.

"I think he's a class bowler, no doubt about it. He's taken a lot of wickets, been the leading wicket-taker for South Africa over a long period of time - and he was tough to face the other day as well. That's how the game goes, sometimes you're batting well and not making runs, sometimes you're bowling well and not getting many wickets," Clarke said. "His statistics show he'll find a way to take wickets. We've just got to find a way to keep him out."

South Africa must win in Port Elizabeth to keep alive its goal of beating Australia in a home series, which it has failed to do in six attempts since its readmission in 1992.

"It's massive. We're the number-one team in the world and it's important for us to go up, now that we're one-nil down," said Morkel.

"It's important for us to stand up and react to what happened last week.

"I know it's going to be tough, but we know now more or less what to expect."

Morkel predicted that if South Africa's batsmen could survive the new ball and string together some solid partnerships - only once did the home team reach a 50-run partnership in Centurion - the team could thrive, without the need for an overhaul of its tactics.

"I think our success over the past couple of years has been playing our brand of cricket and [we should] not change it now. It's important that we don't get caught up with that sort of battle, we stick to the game plans that are going to get us 20 wickets," he said.