Retief Goosen, the 2001 U.S. Open champion, also pulled out Friday, citing a back injury.
Woosnam, the 1991 Masters champion who has played in the last 21 British Opens, withdrew after three holes of his second round at Loch Lomond.
'I have a bad back,' he said. 'I don't know how bad it is. I'll have treatment over the next couple of days.'
Woosnam, a 45-year-old Welshman, had been trying to get into the Open as one of the top eight finishers this week among those players who were not already exempt from qualifying.
Now he faces final qualifying next Sunday and Monday in a bid to keep his British Open streak going.
Goosen is exempt from qualifying for the British Open.
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