Montgomerie will now take on Stewart Cink in the third round

Montgomerie produced a superb back nine to come from behind and beat Charles Howell at the final hole in Tucson.

And in an all-British match, England's Casey recovered from a slow start to beat Welshman Bradley Dredge 2&1.

Ian Poulter, Lee Westwood and Luke Donald all lost, as did world number two Phil Mickelson, the American beaten 2&1 by Australia's Stuart Appleby.

Tiger Woods progressed to the last 16 with a comfortable 3&2 win over Arron Oberholser.

It was an agonising defeat for Englishman Poulter, who fought back from three down after 14 holes against KJ Choi, only to lose by bogeying the first extra hole to the South Korean's par.

My caddie said, 'right, it's Ryder Cup mode' Colin Montgomerie

Fellow Englishman Westwood was never ahead in his match as he went down 2&1 to Justin Leonard, and it was a similar story for compatriot Donald in a 2&1 defeat to US Open champion Angel Cabrera.

Montgomerie birdied three out of four holes to take the lead from Howell on the back nine and put himself in position to win.

The Scotsman said: "Charles birdied the 11th to go all square and my caddie said, 'right, Mr Montgomerie, it's Ryder Cup mode'.

"I was four under from then on, so he should say that more often in stroke-play events.

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"We're in the last 16 and delighted. I look forward to playing again tomorrow."

Montgomerie will take on Stewart Cink on Friday after the American came from behind to win two up against Open champion Padraig Harrington.

Australia's Aaron Baddeley was the first player through on the day as his second round opponent David Toms withdrew with a back injury.

And, in a remarkable end to the day, defending champion Henrik Stenson went to the seventh extra hole with Trevor Immelman before finally sinking a birdie to his opponent's par to progress.

Thursday's second round results:

Adam Scott (Aus) v Woody Austin (US)
Austin won at first extra hole

Sergio Garcia (Spa) v Boo Weekley (US)
Weekley won 3&1

Colin Montgomerie (Sco) v Charles Howell (US)
Montgomerie won 1 up

Padraig Harrington (Ire) v Stewart Cink (US)
Cink won 2 up

Bradley Dredge (Wal) v Paul Casey (Eng)
Casey won 2&1

KJ Choi (Kor) v Ian Poulter (Eng)
Choi won at first extra hole

Rod Pampling (Aus) v Nick O'Hern (Aus)
Pampling won 5&4

Vijay Singh (Fij) v Niclas Fasth (Swe)
Singh won 1 up

Jonathan Byrd (US) v Andres Romero (Arg)
Byrd won 6&4

Henrik Stenson (Swe) v Trevor Immelman (SA)
Stenson won at seventh extra hole

Steve Stricker (US) v Hunter Mahan (US)
Stricker won at second extra hole

Angel Cabrera (Arg) v Luke Donald (Eng)
Cabrera won 2&1

Tiger Woods (US) v Arron Oberholser (US)
Woods won 3&2

David Toms (US) v Aaron Baddeley (Aus)
Baddeley through after Toms forfeits

Phil Mickelson (US) v Stuart Appleby (Aus)
Appleby won 2&1