The 26-year-old Glover is currently 14th in the US Ryder Cup list

R1 LEADERBOARD:
US unless stated
-6 L Glover, C Riley
-5 B Andrade
-4 S Cink, R Allenby (Aus), L Donald (Eng), JJ Henry, H Stenson (Swe), D Love III
Selected others:
-3 L Westwood (Eng), P Mickelson, T Woods, G Ogilvy (Aus), S Garcia
-2 K Ferrie (Eng), I Poulter (Eng)

American Ryder Cup candidates Lucas Glover and Chris Riley upstaged the clash of Tiger Woods and Phil Mickelson to lead the way at Medinah on Thursday.

The USPGA is the last counting event in the selection process for the US team to face Europe and the leaderboard is full of players desperate for points.

Glover and Riley are one shot clear of Billy Andrade after six-under 66s.

A shot back on four under are six players including England's Luke Donald and Swedish star Henrik Stenson.

Donald, dressed in black in memory of Darren Clarke's wife Heather who was buried on Thursday, bogeyed the last but was happy to be in contention.

We all missed a few shots, got up and down and grinded our way around the golf course Tiger Woods

"The last three majors I struggled with the first round, so it's nice be in the 60s," said Donald.

And Stenson's return to form will delight European Ryder Cup captain Ian Woosnam after an untidy couple of months.

Alongside these two in a tie for fourth are three more Americans with Ryder Cup pretensions - Stewart Cink, JJ Henry and Davis Love III - and Australia's Robert Allenby.

Cink, a captain's pick in 2004, is 12th in the current American list, Henry is in eighth place and Love is back in 15th, one place behind co-leader Glover, who has never made a cut at a major before.

Asked afterwards if has been thinking about the Ryder Cup, the 26-year-old Glover, who carded eight birdies and two bogeys, said: "Every day, every minute, every second for the last six months.

"I decided to put that behind me this week and try to just play golf, have fun, not worry about it. Play well and let it take care of itself."

Andrade, in third place after a 67, is 33rd on the points list but a top-two finish could be enough for a spot in captain Tom Lehman's team. He is only in the tournament because Steve Elkington pulled out at the last minute.

It was impossible to separate golf's two biggest stars on Thursday

It could have been so much better for Love, the 1997 USPGA champion, as he was seven under after 14 - having gone out in 30 shots - before a triple-bogey at the short 17th dragged him back.

One shot behind this group are a host of big names, most notably the day's star turns Woods, Mickelson and playing partner Geoff Ogilvy, the US Open champion.

It is a USPGA tradition to put the year's major champions together for the first 36 holes but rarely can the organisers have stumbled upon such an eagerly anticipated showdown as Woods v Mickelson.

With so much at stake it is hardly surprising that neither man was at his very best as both rolled their sleeves up to card three-under 69s.

Woods started with a bogey and was three shots behind his great rival after two holes as the 36-year-old Mickelson made back-to-back birdies.

But Mickelson then started to struggle with his driver while the 30-year-old Woods knuckled down without ever really catching fire.

"We played OK but we both had chances to go lower," said Mickelson, the defending champion and world number two.

Woods, who is chasing a sixth win this season and 12th major title, said: "I was behind the eight ball early, but we all missed a few shots, got up and down and grinded our way around the golf course."

England's Donald is only two off the lead after a steady 68

Ogilvy, who himself admitted he was "just along for the ride", also carded a 69 and all three will feel they are excellently placed for a tilt at a second major title this season.

Also in contention on three under are Ryder Cup partners Sergio Garcia and Lee Westwood.

The 33-year-old Englishman had to be persuaded to play this week by his great friend Clarke and was among a number of players greatly moved by the prayer service for Heather Clarke led by Lehman before play started.

Another on three under is Billy Mayfair, a man who has had his own cancer scare.

The American, who had surgery for testicular cancer only two weeks ago, was six under through 11 before late bogeys brought him back into the chasing pack.

Other big names very much in the hunt are world number five Retief Goosen, 2005 US Open champion Michael Campbell, world number three Jim Furyk and England's Ian Poulter.

They are all on two under, one better than the likes of world number six Adam Scott, number eight Ernie Els and 10th-ranked David Howell, the European Order of Merit leader.

But among those in danger of missing the cut on Friday are last year's European number one Colin Montgomerie, who carded a 77, and Padraig Harrington.

The Irishman, whose wife attended Heather Clarke's funeral in Antrim, is on three over, the same score American Olin Browne managed despite a hole-in-one at the short 17th.