World number 267 Roberto Castro took a three-shot lead into the second round of the prestigious Players Championship, but a quick glance at the leaderboard put his chances of a first PGA Tour title on Sunday into stark perspective.

Castro carded an eagle and seven birdies in a nine-under-par 63 at Sawgrass to match the course record set by Fred Couples in 1992 and equalled by Greg Norman two years later.

And with world number 1,207 Derek Ernst winning the Wells Fargo Championship last weekend, the 27-year-old American could be forgiven for dreaming of claiming the first prize of just over $1million this weekend.

However, world number two Rory McIlroy shot a flawless 66 to share second place with former Masters champion Zach Johnson, while Tiger Woods was set to do the same until his only bogey of the day on the 18th.

Woods, who replaced McIlroy at the top of the rankings earlier this year, had never had a bogey-free round in 55 previous attempts in the tournament, but at least carded a five-under 67, his first sub-70 opening round in the event.

Padraig Harrington is five off the lead after a rounds 68, while Graeme McDowell shot a two-under 70. 

Rory McIlroy

Castro, who has made just seven cuts in 14 events this season, said: "It was a lot of fun. First time around here I was pretty nervous on the 17th, but birdied 17 and 18 which got things rolling into the front nine.

"Something solid was what I was hoping for. I'm usually really good at getting myself way out of it and having to dig myself out of a hole."

McIlroy was probably also hoping for something solid and duly reaped the benefits of a conservative approach after missing the cut in his previous three appearances in golf's 'unofficial fifth major' with a scoring average of 74.

"I made a couple of good par saves, but apart from that I was giving myself a lot of chances for birdie" - Rory McIlroy

The 24-year-old told Sky Sports 2: "It's my best score around this course by a long way so I'm very happy. I kept my ball in play for the most part and didn't make any stupid mistakes.

"I made a couple of good par saves, but apart from that I was giving myself a lot of chances for birdie. If I can continue doing that over the next three days I should be there or thereabouts going into Sunday.

"You have to find the balance between being conservative but also aggressive as well. I adopted quite a conservative strategy off the tee this week because I feel my iron play has been so good. Even if I leave myself a bit further back I am still giving myself good chances for birdies."

Sergio Garcia is also five off the lead after a 68, while Lee Westwood matched the 69 of Masters champion Adam Scott.