English world No 3 Lee Westwood needed to find an emergency replacement for his caddie for the Wells Fargo Championship after Billy Foster hurt his knee in a charity soccer game.

Westwood doesn’t expect his usual bagman will be back in action until just before the US Open in mid-June, so it must be pretty serious.

"He put his foot down wrong and has torn something in his knee," Westwood said.

"He's out probably four weeks minimum, depending on the (MRI) scan that he's having on Friday when he gets back to England.

"He's set a goal for the PGA Championship at Wentworth, which is two-and-a-half weeks' time, but I think the Scandinavian Masters in Sweden the week before the US Open is probably more realistic."

Westwood and Foster have shared a successful partnership since they first hooked up for the Irish Open three years ago, including the Englishman being elevated to the No 1 ranking in men’s golf.

"He knows my game really well," Westwood said. "It'll be a loss for a few weeks, but accidents happen. He goes skiing twice a year and he's never done anything like that, and then he puts his foot down wrong on a football field having a kick around.

"But I've been out here a long time. This is not my first rodeo. I think I'll be able to cope."

Foster’s replacement will be Casey Kerr, who has most recently worked for 1992 Masters champion Fred Couples.

"Casey is a good caddie," said Westwood. "He's proved that. He caddied for Fred and a lot of other good players. Fred was up there in the Masters (last month), so he's been in big arenas in contention."

Westwood arrives at Quail Hollow in good form having successfully defended his Indonesia Open title and could once again be crowned the No 1 golfer in the world if he wins the Wells Fargo Championship.

However, the 39-year-old has more other things on his mind.

"It's not really a priority," Westwood said. "I'd obviously like to be world No 1 again, but winning major championships is really my priority from now on.

"If I did that, then I think world No 1 would come as a consequence," he said. "Winning this week is the priority."