Second round leaderboard:
-12 L Westwood (Eng) -11 R Imada (Jap), F Molinari (Ita), H Slocum (US) -9 L Glover (US) -8 R Allenby (Aus), C Hoffman (US), B Crane (US), L Donald (Eng) Selected others: -7 G McDowell (NI) -5 S Garcia (Spa) -4 O Wilson (Eng) -3 T Woods (US), P Mickelson (US) Missed the cut: -1 I Poulter (Eng), B Davis (Eng), P Casey (Eng) level J Rose (Eng), G Owen (Eng), R Fisher (Eng) +1 P Harrington (Ire), R McIlroy (NI), E Els (SA) +4 M Laird (Sco)
Westwood plays his approach to the 18th, where a shot dropped cuts his lead
Lee Westwood shot a superb seven-under-par 65 to lead by one shot at halfway in the Players Championship.
The Masters runner-up, who carded 67 on Thursday, made six birdies and an eagle on the 16th but bogeyed the par-four last for 12 under at Sawgrass.
Ryuji Imada (66), Francesco Molinari (65) and Heath Slocum (66) were tied for second, one stroke behind.
Tiger Woods and Phil Mickelson both carded 71 to finish three under but Rory McIlroy (+1) missed the cut.
Woods, who made a double bogey on the 14th, can lose his world number one status to Mickelson if his American rival wins and Woods finishes worse than fifth but the pair are both back in a tie for 46th.
And they lie nine shots behind Westwood, who has recorded top-three finishes in the last three majors and started the day with three consecutive birdies.
Westwood, on the brink of moving third in the world rankings, was five under for the day through 12 before eagling the long 16th, but although a further birdie came at the infamous short 17th a bogey at the last pegged him back.
"I'm playing some of the best golf of my life, so I'm very, very relaxed out there," said Westwood.
And the Worksop golfer believes he is in the right frame of mind to go one better than he did last month when finishing second to Mickelson at Augusta.
"As you get older, it gets harder to peak all the time when you want to so you have to pick and choose your ones," said the 37-year-old, whose only PGA Tour victory came at the 1998 New Orleans Classic.
"You want to play well in the biggest tournaments and this is one of the biggest tournaments. A Players victory would be incredibly important."
Woods, playing only his third event since taking five months off following revelations about his private life, found only eight of 14 fairways and admitted his accuracy was slightly off.
"I wasn't quite as sharp today as I was yesterday," said the 14-time major champion.
"I felt like I putted better but unfortunately I was just a little bit too far away from the holes. Most of the putts I had were just outside that birdie range."
Woods reflects on another wayward tee shot
A week after missing the cut by eight shots at the Quail Hollow Championship in North Carolina, Woods avoided the embarrassment of a second consecutive early exit for the first time in his career.
"I've just got to keep plodding along," he said. "On this golf course anything can happen. You can make some big numbers here quick."
England's Luke Donald, who was joint third overnight, lost three places against the field but kept moving in the right direction with a 69 to edge to eight under.
Northern Ireland's Graeme McDowell improved dramatically on his opening 72 to match Westwood's round-of-the-day 65 to improve to seven under.
Northern Ireland's McIlroy, whose victory at Quail Hollow made him the youngest winner on the Tour since Tiger Woods in 1996, admitted he never got going in rounds of 73 and 72.
"I felt I hit it good all week and putted well - there were just a couple of slack shots here and there cost me a chance of playing on the weekend," he said.
"I tried hard on every shot. I just didn't have it. The course doesn't really fit my eye that well."
England's Ian Poulter and Brian Davis missed the cut by one after both shooting 71 for one under, their fate sealed by John Merrick's rare birdie at the last which moved the cut-off point to two under, while countrymen Justin Rose, Greg Owen and Ross Fisher all ended level par.
Ireland's three-time major champion Padraig Harrington and South African Ernie Els, a two-time winner this season, also missed the cut by three.
I apologise to all the TV viewers
Phil Mickelson after a round short of highlights
Of those chasing Westwood, Molinari was justifiably delighted with a round that saw him hit every green in regulation.
The 27-year-old, who skipped his home Italian Open to make his debut at Sawgrass, said: "Today was just amazing. I'm hitting the ball really well at the moment.
"I just have to be patient and take the chances I have. I was enjoying my week and I'm enjoying it a lot now, obviously."
Imada, the only Japanese player in the field, drained a lengthy putt on the first to save par, a moment that would set the tone for his round.
"To have 23 putts, everything has got to go your way," he said.
"My putting feels great. I don't know the last time it felt this good."
Mickelson was less enamoured with his own efforts, admitting: "It was the boringest round to watch. I apologize to all the TV viewers."
However, the 40-year-old added that everyone in the field was still in with a chance of winning.
"Because the character of the course is changing so much from the morning to the afternoon, the guys that are two, three or four under par are in the tournament," he said.
"If they shoot six under par they're going to move right up the leaderboard and it's going to be difficult for the leaders to pull away."