Reigning British Open champion Darren Clarke is battling a groin strain at the Shell Houston Open, the Associated Press reports. Clarke, whose last victory in the U.S. came at the 2003 World Golf Championships-Bridgestone Invitational, told the AP that he felt the injury early in his round and it got progressively worse as the day went on. While Clarke noted that rest was the best remedy for his injury, he wasn't thinking about withdrawing from this week's event at Redstone Golf Club. "I wanted to keep going, keep going and keep going as I need to play all four rounds before the Masters," he told the AP. Clarke is making his fifth career start in the Shell Houston Open. After posting a second-place and a T4 finish in 2002 and 2005, he played just three rounds in his next two appearances. The Northern Irishman shot 72-71 in his first two rounds this week. At 1 under, he’s one shot outside the projected cutline and may not have a choice about whether or not he’ll be resting his injury this weekend.