Injured champion Danny Willett's grip loosened on Nedbank Challenge title

Defending champion Willett was in obvious distress from the recurrence of a long-standing back injury during his round.

After playing the first five holes in four over, he lay down on the sixth fairway and performed stretching exercises before receiving treatment from the European Tour physiotherapist on the ninth tee.

This certainly appeared to help as the world No 20 pitched to 15 feet on the par-5 hole for his first birdie of the day, and the weather delay which followed allowed him to receive further treatment before covering the back nine in 35.

Willett had reached the turn in four-over 40 while Fitzpatrick also stood four over for his round, through 11 holes, when play was suspended at the Gary Player Country Club in Sun City, South Africa.

Twenty-eight-year-old Willett - who had birdied the ninth after three bogeys and a double bogey at the 449-yard par-4 third - came back in one under thanks to eight pars and a birdie at 16.

He went for more treatment immediately after his round.

However, after rounds of 67 and 75 he has fallen nine shots off the lead held by Sweden's Henrik Stenson (66 67).

Fitzpatrick dropped a further shot on resumption of play to add a 77 to his opening 69 and will look for a good weekend to pull him clear of the lower places in the 30-man field.

Stenson, meanwhile, produced a storming finish to claim the lead at the halfway stage.

Shortly after play resumed following the delay, the Swede trailed playing partner and local favourite Jaco van Zyl by three shots with seven holes to play.

However, the world No 7, who rated his chances of simply playing in the event at five per cent after spending three days in bed with flu, rolled in a hat-trick of birdies from the 13th and picked up another shot on the 17th to add a 67 to his opening 66.

At 11 under par Stenson was one shot ahead of van Zyl, who had started his round birdie, eagle before eventually settling for a 68, with American Robert Streb another shot back following a 66, the lowest round of the day.

"I'm surprised given that on Wednesday afternoon I didn't think I would be able to tee it up," Stenson admitted.

"I thought I was done and dusted, so to be leading after two days it's a turnaround to say the least. But the saying is 'Beware of the injured or sick golfer' and I guess that's true.

"I just tried to stay patient and get round and I've done that pretty well so far. I'm getting over the virus, but I was more fatigued this morning than I was yesterday just because of playing yesterday. It takes a lot out of you playing in 35 to 40 degrees when you're not physically well.

"I'm heading in the right direction, but I'm not getting a chance to rest up much. Tomorrow I'll probably have very heavy legs again, but being in the hunt for a tournament should get me going and hopefully that will kickstart it tomorrow."

Stenson had followed three birdies in the first five holes with a hat-trick of bogeys from the sixth and admitted that the delay caused by the threat of lightning came at the right time.

The 39-year-old, who was on the 10th hole at the time along with Willett, said: "I was not on a good run before the break. I didn't do too much wrong but managed to string three bogeys in a row, so at that time it was probably good to have a break and it really cooled down afterwards for the back nine.

"I got the putter going - that was hot at least - and made a couple of nice birdie putts. All in all a very good back nine turned an average round into a good one."