Justin Rose is in sight of becoming the European Tour's youngest number one for 18 years after a rollercoaster ride in the third round of the Volvo Masters at Valderrama today, but the defending champion Padraig Harrington might still have his say on proceedings.

Rose started the season-ending event third in the standings behind leader Ernie Els and Harrington in second, but the 27-year-old will now go into tomorrow's final round in the driving seat as he holds a four-stroke lead over Harrington and Yorkshire's Simon Dyson who share second. Els opted to play in  Singapore - where he missed the cut - instead of Spain.

Playing together for the second time in three days, Open champion Harrington and Rose both returned 71s to remain four under and level par respectively, but it was not as straightforward as that. Anything but, in fact.

Harrington, four behind at the halfway stage, incredibly cancelled that out in just two holes when he birdied the first while Rose followed an opening bogey with a sloppy double-bogey.

For all the world, it looked as if Rose had lost his way in pursuit of the money-list crown and his first tournament win since last November's Australian Masters.

"I was a little bit shell-shocked after the start," admitted Rose. "It was certainly not what the doctor ordered, but on the third tee I told myself I was still leading.

"I said yesterday that a four-shot lead at halfway is nothing to get excited about and I proved it. But I survived today. It was a great day to get round in level par and maintain a four-shot lead.

Rose was almost in the lake on the long fourth, but after escaping there with a par five he settled down. In fact, after the dropped shots at the first two holes he covered 16 holes in three under with birdies at the eighth, 10th and 11th.

In turn Harrington began to struggle with his game in parts.with bogeys at seven and 13, but the 36-year-old never gives up and he rallied well with a fine birdie at 17 and a closing par to ensure he didn't lose ground on the leader.

"Justin came back very well from that start. I can't now get away with having a bad day, whereas he can still win not having a good day," said Harrington, knowing Rose has the edge. "It's kind of in his hands tomorrow."

Graeme McDowell and Paul McGinley both shot three over 74s and both remain in the top 10. The Portrush pro is tied for eighth on four over while McGinley is a shot further back, tied 10th.