Darren Clarke has admitted he has become frustrated with his form after failing to build on his British Open triumph in 2011.
The Northern Irishman won at Sandwich last year by three shots to win his first major title, but he heads into this year's tournament at Royal Lytham out of form.
Clarke said: "I play to win golf tournaments but I have been nowhere near that standard for quite some time.
"I have been practising and doing all of the right things, but it just hasn't clicked so far."
Clarke's best performance of the year came at the Volvo Golf Champions, where he finished 20th.
