Barring an extraordinarily collapse by either player, Rory McIlroy and Keegan Bradley will shoot it out for the PGA Grand Slam today.Tied on four-under-par going into the final round, the two will battle in a winner-takes-all 18 holes at Port Royal Golf Course.More than likely Charl Schwartzel and Darren Clarke will fight for third as the pair both struggled yesterday. Schwartzel shot a three-over 74 while Clarke finds himself a further three shots back after his opening round 67.Coming from behind to deny McIlroy is not an alien concept to Schwartzel, however, and today's weather conditions could yet play the most important role, with wind gusts of 20 to 30 mph expected to hit the Island.McIlroy will also need to get his putting under control if he is to become the tournament's youngest winner since Tiger Woods beat Vijay Singh to the title in 1998 as a 22-year-old.The Northern Irishman struggled on the greens yesterday and missed three times from within 10 feet for birdie in the opening six holes.Birdies at five, when he nearly drove the green on the 380-yard par four, and again at seven when he missed a short putt for eagle, at least kept him in sight of Bradley on the front nine, who was five-under at that stage.“It was getting a little bit frustrating,” said McIlroy, “because I was reading them, and every time . . . I felt as if I was hitting the putt on the line I wanted to, but it was just going nowhere near the hole.“The greens that I have been putting on the last couple of weeks have been a little different to the greens here. I had not really been factoring in the grain as much but it plays a huge part on these greens.“I finished really, really well . . . so to draw level with him (Bradley) after the first day was nice.”Bradley had no such troubles and his flying start was propelled by eagles at the par-five second and seventh. The PGA Champion hit six-iron approaches to within two feet at both and he called the one to seven 'the best shot I've ever hit in my life'.While the six-iron to seven was probably the highlight of his round, a 20-foot putt for bogey at the first hole really set the tone for a front nine when Bradley just couldn't seem to miss once he hit the green.Bradley's long putting came to his rescue at the par-three eighth when he drained a 30-footer to save par and a birdie at nine gave him a four shot lead over the field.At six-under through 11, Bradley had a five-shot lead on McIlroy, who three-putted the same hole and dropped back to one-under as his woes on the greens continued.The momentum shifted slightly on 12 when McIlroy sunk a 30-footer for birdie and Bradley, who hit his approach long could only get up and down for par.Bradley dropped a shot at 14 when he missed from a foot, and with McIlroy birdieing the same hole the two-shot swing changed the complexion of the round.McIlroy crushed another drive down 15, which saw him finish just 10 yards short of the green on the 412-yard par-four. That set-up another birdie opportunity, which he took, closing the gap on Bradley to just two shots.The defining moment for the round came on the par-three 16, when McIlroy was the only one of the foursome to hit the green and although he walked away with a par, Bradley's bogey closed the gap to one shot.Schwartzel and Clarke, meanwhile, both hit their first tee shots into the sea, and walked away with triple-bogeys.McIlroy's strong finish continued on 17 when he made birdie on the back of another solid drive as the rain hammered down.“I gave myself so many chances on the front nine and didn't really make anything,” he said. “I started to hole some putts on the back nine and played very, very well. It was a bonus to par 16 and birdie 17 in that bad weather.”The trophy is likely to be a two-horse race as Schwartzel and Clarke will be hoping to give some respectability to their scorecards.Clarke was typically blunt in describing his round as ‘crap', and said he hadn't come to Bermuda to ‘play that badly'.A round that never really got going saw Clarke slip to three-over after the first four holes and despite birdies at six and seven, Clarke dropped another shot at the par-three eighth, when his tee shot finished in the left hand bunker, and he reached the turn at two-over.The Northern Irishman's troubles at 16 largely summed up his round and bogey on the last completed a miserable start to Clarke's Grand Slam.Schwartzel, meanwhile, kept pace with McIlroy for a while, but a terrible run saw him go from two-under to three-over in the space of four holes from 12 to 16. The triple bogey at the signature par-three completing a collapse which has all but ruled him out of the running.“It's disappointing,” he said, “I thought I actually played really well up until 12, I hardly missed a shot. I'm pretty disappointed, I thought I played much better.”* For pictures of the action click here.