Andalucia Masters third round leaderboard:
-6 G McDowell (NI) G Maybin (NI) -2 D McGrane (Ire) MA Jimenez (Spa) -1 S Garcia (Spa) T Bjorn (Den) Selected others:+3 M Kaymer (Ger) R Fisher (Eng) +2 F Molinari (Ita) +4 D Clarke (NI) +5 JM Olazabal (Spa) +7 E Molinari (Ita)
Kaymer had three birdies and two bogeys
Lee Westwood appears all but certain to become world number one with his top-spot rival Martin Kaymer languishing well down the Andalucia Masters field.
German Kaymer needs a top-two finish at Valderrama to stop Westwood ending Tiger Woods's 281-week reign.
But a third-round 70 left Kaymer three over par, nine shots behind Northern Ireland's co-leaders Graeme McDowell and Gareth Maybin.
Barring a freak final round, England's Westwood will topple Woods on Sunday.
The 37-year-old is currently recovering from a calf problem and does not intend to play again before the WGC-HSBC Champions event on 4 November.
He would become Europe's first number one golfer since Nick Faldo in 1994.
Kaymer had started the day 11 shots off McDowell's lead after opening with a 72 on Thursday and following that up with a 75 in his second round.
The 25-year-old, therefore, required a sensational effort on Saturday to move up the leaderboard.
However, the USPGA champion had to be content with merely playing solidly in blustery conditions, picking up only one shot - on the fourth hole - to reach the turn in 34.
He sank two more birdies at 14 and 17 but bogeys on 15 and 18 extinguished any slim hope he had of moving into contention.
US Open champion McDowell had two double bogeys in his one-over round of 72, at the seventh and 18th, and while Maybin dropped shots at the first and second holes he improved with three birdies before the turn and then had pars all the way home.
"I'd had a stretch of holes when I was all over the place but then I steadied the ship and I stood on the 18th tee thinking 'let's just get the job done'," said McDowell. "But it was one of those careless finishes.
"The weather's spread-eagled the field, but Gareth's going to be a tough opponent."
Ireland's Damien McGrane (70) shared third place with Spain's Miguel Angel Jimenez (71) on two under.
Sergio Garcia showed encouraging form with a round of 69 to move into a share of fifth place with Thomas Bjorn, who had four early birdies and four bogeys in a 71.
Sweden's Niclas Fasth dropped from third to 13th after following Friday's 66 with a 76, but is still one shot ahead of Kaymer.
Kaymer has the consolation of leading the European Tour money list, the Race to Dubai, from McDowell by almost a million euros with five events to be decided.
But it is likely that US Open champion McDowell will close that gap significantly on Sunday with 500,000 euros going to the winner in Andalucia.