* Scott birdies the last to stretch lead
* McIlroy rallies after patchy front nine (Adds quotes, detail)
By Nick Mulvenney
SYDNEY, Nov 30 (Reuters) - Adam Scott holds the upper hand in his duel with Rory McIlroy going into the final day of the Australian Open after the home favourite posted a four-under-par 68 to open a four-shot lead over the Briton on Saturday.
Two-time major champion McIlroy looked down and out after a patchy front nine but rallied for a 70 to remain in the hunt for his first win of the year in front of bumper galleries at the Royal Sydney Golf Course.
Most of the crowd were backing Scott's bid to secure a "triple crown" of Australian titles and a huge cheer went around the course when he birdied the last to double his overnight lead by reaching 16-under for the tournament.
"It's an exciting position to be in, obviously a great chance to win my national championship tomorrow," Scott, who has already won the Australian PGA and Masters titles this month, told reporters.
"And then also win the three events down here which is an unbelievable spot to be in. If you'd told me a month ago, I wouldn't have believed you.
"One round to go but a lot can happen. It's a phenomenon playing behind me and I'm sure he's going to throw plenty at me... but as long as the eye stays in with the putter, I think I should hold on."
McIlroy missed a shorter birdie putt at the 18th and so will resume on Sunday on 12-under, four shots clear of Australians Max McCardle (69), Matt Jones (72) and Richard Green (73) in a share of third.
"I played a good back nine, it could have been a couple better, I felt I left a couple out there," the 24-year-old said.
"But obviously I'm four back now and I've got a tough job on my hands to try and catch Adam."
Scott started the day with a two-shot advantage over McIlroy and, with the sun shining brightly, it looked being a day of low scoring when both players birdied the opening hole.
McIlroy found himself in a thicket with his drive at the second but rallied to save par brilliantly as Scott lipped out with a birdie putt.
The Northern Irishman's bogey at the fourth was not a disaster as Scott followed suit after finding a bunker but the Australian opened up a four-shot lead as the wind whipped up at the fifth.
McIlroy undercooked successive chips from the bottom of a greenside slope and then two-putted for a double bogey, while Scott missed a 10-foot birdie putt but sank his second attempt from a foot for par.
Former world number one McIlroy was now buried in the chasing pack and when Scott picked up shots at the three holes before the turn he moved to 15-under, five clear of Jones and Green in second.
Scott drove into the trees and then the sand to take a bogey at the 10th, however, and McIlroy capitalised with the first of three birdies in five holes, the last coming after he hit the pin with his tee shot at the short 14th.
Scott was only a little less accurate with his iron for a birdie at the same hole and the marquee pairing were now clear at the top of the leaderboard.
Both found the greenside bunkers at the 16th but saved par, McIlroy just missing out on a birdie with a long snaking putt, and the pair got up-and-down from off the green for pars at the next before Scott drained his crucial five-footer at the last.
"I had to make (my putt) because I believed he would make his," Scott added.
"If it went the other way and I missed and he made, it's two shots and that's nothing. That can be gone on the first green tomorrow. Four shots is a slightly better buffer."
McIlroy, who has endured a disappointing season after a stellar 2012, lamented his miss with the putter at the 18th but has not given up hopes of overhauling his Australian friend.
"(It's possible) on this golf course, where there can be a lot of two-shot swings and someone makes a couple of pars and someone gets off to a fast start and makes a birdie and an eagle and you're right back in it," McIlroy said.
"There's plenty of chances out there and it's just a matter of taking your opportunities when they come." (Editing by John O'Brien)