World number two Phil Mickelson admitted he has improvements to make in his game after a second-round 77 saw him make an early exit from the Open Championship at Carnoustie.

Mickelson's six-over-par total after yesterday's 71 was too many to survive the cut and the 37-year-old knew it.

He has complained about his putting all week and yesterday was no different, giving the left-hander plenty to think about.

''There were some under-par scores out there but I just didn't putt well enough to have one of them,'' said Mickelson, who last week lost the Scottish Open in a play-off having squandered a three-shot lead early in the final round. ''They are very good greens and I have seen a lot of guys make putts, I just haven't been one of them.

Mickelson's round was anything but ordinary with just one birdie, five bogeys and double-bogey six at the last.

But the real talking point came early in his round when, at the second, there was some confusion over a ruling.

His approach to the 463-yard hole became plugged in the rough and, after initially thinking he was entitled to a free drop, he took a penalty. But when the ball was dropped on the top of a hill it would not stop still.

Having eventually been placed the ball held its spot for a few seconds before trundling off down the slope in the direction of the green, coming to a halt 15 feet closer and all entirely legal.

''It was an embedded ball and this is the only week that it has to be on the closely-cut area,'' explained Mickelson on the difference of the R&A rules referring to plugged balls.

''Both the referee and I were off a little bit (on the rules). But in the end it was an accurate ruling. We are just not used to it.''