JOHANNESBURG, South Africa (AFP) — World number two Rory McIlroy defied severe back pain to fire a second-round 68 yesterday and trail South African Open leader, Graeme Storm by three shots.

McIlroy admitted, after his roller coaster trek around the Glendower Golf Club near Johannesburg, that he considered withdrawing from the European Tour event.

“I thought about pulling out before teeing off today (Friday),” the 27-year-old from Northern Ireland told reporters.

“I tweaked my back somehow and was not very comfortable playing the first few shots of my second round.

“I am going to get some treatment now and hopefully everything will be okay by the time I tee off tomorrow (Saturday).

McIlroy, second in the world rankings behind Australian Jason Day, carded the four-under 68, despite bogeying the final two holes.

The round of the four-time major winner included an eagle, seven birdies, six pars, three bogeys and a double bogey.

At one stage during the second day, McIlroy trailed 38-year-old Englishman Storm by nine strokes, then played eight holes from the eighth in eight under, needing just eight putts.

After a par at 16, however, McIlroy dropped a shot at 17 and another at 18, both par fours, having been poised to overtake one-time European Tour winner, Storm.

The Englishman carded a course record-equalling 63 for a two-round total of 132, after starting with a 69 over the 6,942-metre (7,100-yard) parkland track.

Storm carded five birdies on the front nine and four more on the second nine, without dropping a shot on a course packed with water hazards.

“Obviously, it is great to shoot a round like that,” said the golfer ranked 251 in the world, “but there was a tinge of disappointment when I failed to hole a long, last-hole birdie putt.

“That would have given me a course record 62 and also equalled my lowest score in South Africa.

“The putter was my hottest club for the second-successive day. It was hot yesterday and it was hot today.

“To shoot 63 and birdie only one of the (three) par fives tells me that I played pretty good golf.”

South Africans Trevor Fisher Junior (68) and Jbe Kruger (67), and American Peter Uihlein (64) share second place on 134, two shots off the pace.

McIlroy, English pair Laurie Canter (66) and Jordan Smith (66), Scot David Drysdale (65) and South African Keith Horne (69) are all one stroke further back on 135.

A late afternoon storm halted play for the day with a few golfers still on the course, but none were threatening to alter the top of the leader board.

They will resume play at 0715 local time (0515 GMT) Saturday before the third round begins.

Of the five former major winners competing, only McIlroy is guaranteed to be involved in the final two rounds.

Ernie Els (70) of South Africa is on 144, Nick Faldo (75) of England on 145 and Darren Clarke of Northern Ireland was four over for the tournament with one hole to play.

While Retief Goosen of South Africa atoned for a disastrous opening 80 with a 71 Friday, he is certain to miss the cut.

Defending champion Brandon Stone of South Africa improved his first-round score by seven shots, with a 67 to trail Storm by nine shots.