So far, the principals have followed the script to perfection. If this were an old-style western, you could just imagine the two gunslingers shooting it out. Except, in this instance, rather than revolvers, Justin Rose and Pádraig Harrington will use an array of drivers, irons and putters to decide their duel over the final 36 holes of the Volvo Masters.

The incentive is enormous. Win the tournament, and you win the European Tour Order of Merit too. Yesterday, as the strong wind again made the course at Valderrama as tough a proposition as players have encountered all year on tour, Rose, chasing his first win of the year, gained the upper hand with a second-round 68 to reach the midpoint on 138, four-under, for a four-stroke lead over Harrington, who finished the day alone in second place.

Now, though, it really gets interesting. "It's very much game on," said Harrington, who shot a second successive 71. "Justin does seem to be playing very well and he's probably hungry for a win. I think he's very hungry for a win in terms of the fact that he's had a great year without winning and would probably like to cap it off with a win."

He added: "Obviously, I've got to manage my own golf for the next two days and try to move forward. Four shots is substantial. I hope that we're playing for first and second and, if that's the case, I'll take my chances with 36 holes to go. The main thing is not that Justin is four ahead of me, which is an issue, but that I am still in the tournament. I'm second at the moment, and I can venture on from here."

With yet more strong winds forecast for the weekend, the European Tour has decided to take the drastic measure of lowering the rough for the final two rounds. Yet, the belief is that the course will still ask tough questions of those chasing the €666,660 top prize, which would be sufficient to enable either Rose or Harrington to leapfrog the absent Ernie Els and claim the money title.

On a day when Rose's 68 was the best round by two shots, overnight leader Graeme McDowell slipped back into a share of third place alongside Miguel Angel Jimenez, Jyoti Randwhawa and Soren Kjeldsen. McDowell failed to find a single birdie, eventually signing for a 75 to be on 143, one-over, while playing partner Paul McGinley also had a horrible time on the greens and finished bogey-bogey for a 75 to drop into a share of seventh place on 144.

Rose, who had suffered from a stomach bug in the first round, was the picture of health yesterday and played superbly. Without a win on tour since capturing the Australian Masters almost 12 months ago, a victory that counted on the 2007 Order of Merit, Rose took a grip on the tournament with a back nine that required just 32 strokes and featured four birdies without dropping a shot.

"I'm just focusing on what I've got to do, trying not to get ahead of myself. I don't want to put any extra pressure on myself, so I'm staying in the moment. That's why I'm playing so well, and that's ultimately the mindset I've got to keep. We're nowhere near the finish line, so I've still got to go about my business, the same old boring stuff, and to take it one shot at a time," said Rose.

Rose's four-stroke lead has given him the initiative, but, just as on Thursday, he will have Harrington for company in today's third round. The British Open champion signed for a 71 yesterday that he felt could and should have been better.

"I'd a lot of chances, especially on the back nine," said Harrington. However, he failed to take any of them, finishing that stretch with a sequence of eight pars from the 10th to the 17th before bogeying the 18th after he attempted to draw the ball into a left-to-right wind to a left-hand pin position. "I can't afford to do that too often," Harrington acknowledged of an aggressive play for which he paid the penalty. "That was a mental error, and just shows you can't get complacent at all."

Up to then, Harrington, pretty much like Rose, had stuck to a strategy of playing for position. For instance, on the seventh and ninth holes, two of the longer par fours, Harrington had left his driver in the bag and used three-wood off the tee, while he used five-wood off the 18th tee before that, allowing an aggressive play to infiltrate his mindset.

"I think Justin has probably got the bit between his teeth . . . but I'll be battling. I'd be battling no matter what the situation is," said Harrington, who is seeking back-to-back European Tour money titles.