DARREN CLARKE is facing a fitness battle to be ready to play in the Masters at Augusta this week.

The British Open champion limped off the course at the Houston Open on Friday, having strained a groin muscle during his second round of 71.

Clarke felt the injury while completing his rain-delayed first round but played on through the pain barrier to complete his second round. His second round of 71 put him one under for the tournament and he missed the cut by one shot.

On completion of his second round in Houston, it was suggested by Clarke’s personal trainer that he attend a local doctor to assess the full extent of his injury. But he declined.

“I’ve had these type of injuries in the past and there’s not much you can do but rest,” insisted Clarke. “It’s a really long walk around this golf course and I could have come in after three to four holes this morning. It seemed okay when I finished my first round today but it just got progressively worse in the second round,” he said.

Hunter Mahan opened a one-stroke lead at the halfway stage of the final round last night. While playing partner and overnight leader Louis Oosthuizen’s challenge completely fell apart, Mahan held his nerve to go a stroke clear of Sweden’s Carl Pettersson, who was also one under for the day. Former British Open winner Oosthuizen was enduring a round to forget, however, as he dropped five shots before the turn.

Elsewhere, Ireland’s Graeme McDowell shot a 77 to finish on a one-over total of 289.