Lee Westwood roared to the top of the leaderboard at The Players Championship as the in-form Englishman hit a dazzling 66 to reach nine under par.

After a second place last week at the Arnold Palmer Invitational, the 47-year-old gave another indication he could be a contender this weekend as he established the clubhouse lead.

Westwood has won twice on the PGA Tour, at the 1998 Freeport-McDermott Classic and 2010 St Jude Classic, and a third title would be a long time in coming.

His girlfriend Helen Storey is also his caddie, and Westwood spoke of her positive influence, calling it "very important".

"I'm a lot less serious and fairly light-hearted," Westwood said on the Golf Channel. "There's lot of smiling going on out there and in life in general.

"We're both having fun out there and not treating it too seriously. Obviously I try 110 per cent. I do all the work off the course, in the gym and a lot of stretching nowadays.

"But when I go out on the golf course I play carefree golf, just not worrying about the consequences and the outcomes.

"I think we all try and go out there and get into the zone, whatever it may be for all of us.

"The zone for me is to go out there and not really having anything going on - just getting the yardage, picking the clubs, seeing the shot and trying to do as good as I can on it."

A birdie at the last capped a bogey-free round for Westwood.

Rory McIlroy's faint hopes of making the cut were over long before he finished his second round, with the 2019 champion following his opening 79 with a front nine of 37 before a double bogey at the par-four 10th left no doubt he would miss the weekend.

McIlroy had been undone by a quadruple-bogey eight at the 18th hole in his opening round, which was far from the worst score on the course.

A day after hitting four balls into the water and making 11 at the par-three 17th, the famous island hole, South Korean Byeong Hun An found the green from the tee this time and went close to a birdie.

He rolled a 16-foot putt to the edge of the hole and tapped in for par, getting a warm reception as he put Thursday's nightmare behind him. Like McIlroy, however, his hopes of making the cut were already shot.