The Open 2013: Zach Johnson leads after first-round 66 at Muirfield

Zach Johnson is the current leader of the 2013 Open, after carding a 66 at Muirfield on Thursday.

The 2007 Masters champion made four birdies and an eagle to finish on five-under par, one ahead of the chasing pack.

Johnson says he putted "really well" and admits the Open is "my favourite tournament to play".

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