McLean carded an eagle and eight birdies with just one dropped shot in a superb round of 64 which was all the more impressive in that it was played in the teeth of a strong south-eastern which blew throughout the afternoon.
One shot behind McLean is Des Terblanche after a 66 in benign morning conditions, and a stroke further off the pace are three young South African tyros ' Jean Hugo (66) Bradford Vaughan (66) and Martin Maritz (67).
Nobody, however, will have missed the looming presence of reigning U.S. Open champion Retief Goosen who is a shot further back after a 66 of his own.
Ernie Els posted a 68 to stand at 6-under, the same score as defending champion Trevor Immelman.
Casualties of the halfway cut ' which fell at level par - included PGA Tour star Rory Sabbatini who crashed to a 78, as well as consistent tour performers Andre Cruse and Desvonde Botes.
'Things went my way today,' McLean said afterwards. 'I made a lot of putts and remained patient. I didnt hit that many fairways and just managed to get the ball in the hole.
'Ive had a tough year, to be honest. I took some time off at the beginning and tried to make a swing change, but when I went back out onto the European Challenge Tour my mind was going crazy and my confidence took a knock.
'I think I hit rock bottom around July, but things have gradually got better since then. When you hit rock bottom the only way is up and Ive never practiced as hard as I did this year. When it gets between your ears, golf is a difficult game, and thats what I allowed to happen.'
Terblanches round included five birdies and an eagle two at the par-4 1st ' his 10th ' when he holed his second shot.
'It was a 9-iron from 146 yards,' Terblanche said. 'I didnt see it go in, but someone up there on the green said it was perfect and obviously it was.'
'I didnt actually play that well yesterday but its got better and better and Im actually hitting it good now. Things are looking good.'
Big-hitting Vaughan, who is one of the most exciting young talents on the Sunshine Tour, blotted his card with a bogey from the middle of the fairway at the relatively straightforward 18th. Remarkably, he was using a new set of irons for the first time, after losing faith in his regular set on Thursday.
'I dont think my manager knew what to say to me,' Vaughan laughed. 'But I told him not to worry and that I knew Id be able to hit them ' and thats what I did.'
Goosen meanwhile was delighted with an improved showing following his 69 in the first round, although still felt that he was not hitting the ball as well as he could around a course that received almost no protection from a strangely muted south-easterly breeze.
'The greens were definitely a lot easier in the morning than they were yesterday afternoon,' Goosen said. 'I actually played worse today but this time managed to sink some putts. On the first nine I only hit three greens in regulation ' I think the holiday swing is setting in.
'Although the wind isnt really blowing, the course actually played harder than the first round with the way its set up. It would be good if the wind got up a little over the weekend ' obviously we dont want gales, but a club or two difference could be interesting. Ive seen one or two of the pin positions for tomorrow and if the wind blows we could have some fun out there.'
The reigning U.S. Open champion also admitted that he was ready for a rest after the most successful year of his career, but one that has clearly taken a huge amount out of the genial man from Pietersburg.
'Im looking forward to the holiday coming up. Its getting to the stage now where Im starting to get a bit frustrated when Im hitting what I think are good shots but I dont get the result that I want.
'Im getting a bit tired and frustrated ' gatvol,' he said. 'But Ill give it my all over the weekend. Only two rounds to go for the year so I might as well try and finish off on a high.'
Full Field Scores from the Vodacom Players Championship