England's Luke Donald faces an uphill task to retain his Madrid Masters title after a poor end to his second round left him five shots off the pace.
The world number one was in good shape at four under after 15 holes, but bogeyed both the 16th and 18th.
This left him six-under and way behind the leader, England's Lee Slattery, who shot an impressive 66 to go 11 under.
This gives the 33-year-old a one-shot lead over Italy's Francesco Molinari and Spain's Eduardo de la Riva.
World number 328 Slattery lost his tour card in 2007 and, at 136th on The Race to Dubai, faces another nervy end to the season this year.
However, after carding an opening round of 67 at El Encin Golf Hotel, he struck even birdies and one bogey on Friday, bouncing back from his only dropped shot at the 12th with a superb long-range birdie putt two holes later.
"I got off to a good start. I was two under early and just kept it together and had a nice finish, birdied the last two holes," said Slattery.
"It's mainly down to putting. I putted very well today, seemed to hole everything. I drove the ball well. On this course you can give it a good smack off the tee and you feel yourself trying to hit it harder and harder.
"I was actually getting too cautious with my game but round here you can't be, you just whack it. This suits me because I just enjoy it and don't think too much - that's the key. I don't think I've ever walked off the course feeling so relaxed."
Donald, who began his defence with an opening round of 68, bogeyed the second hole on Friday but five birdies looked to be handing him another solid round until his late errors.
Donald's fellow Englishman Ross McGowan, who carded 72, remains in contention at eight under, alongside Australia's Brett Rumford, with Italian Lorenzo Gagli a shot better off.
There was also another British success story during the second round in Madrid as Scotland's Elliot Saltman hit a hole-in-one at the par-three third hole to
"I've been trying to lose weight, but now I'm thinking I should have just kept it," said the world number 686, who added: "I don't think they'll let me take that on the plane."