Swede Henrik Stenson was amongst those piling the pressure on Luke Donald as the World Number One continued his bid to top the money lists on both sides of the Atlantic.
Donald, needing a top-two finish to have a chance of overhauling American Webb Simpson, shared the first round lead at the Children's Miracle Network Hospitals Classic in Florida thanks to a six under par 66.
But Stenson, Former Open Champion Justin Leonard and South Korean Bio Kim were all five ahead of the Englishman at the halfway stage.
By the time Donald resumed, Leonard was well on his way to a nine under 63 over the easier Palm course and 21 year old Kim was also 12 under after a 65 on the Magnolia lay-out, including holing out from a bunker on the 14th for birdie.
Stenson made it a three-way tie for the lead when he thrust himself into contention late on with a blemish-free eight under par 64 which included six birdies and an eagle on the 14th.
The trio were five shots ahead of Donald and playing partner Simpson at the midway stage.
Donald started the day two shots ahead of the American, but the pair finished up neck and neck after signing for second rounds of 71 and 69, respectively, on the Magnolia course.
Donald parred the first six holes before missing a short putt at the seventh en route to a bogey which saw him slip further off the pace, but he got back in the red for the day with birdies on the tenth and 12th.
Another dropped shot followed at the par five 14th and, although he immediately cancelled that out with a birdie two on the 15th, he had to settle for a one under 71.
Simpson, meanwhile, birdied the long fourth and sixth to move alongside the European Ryder Cup star.
A mixed back nine - birdies on the 11th and 18th sandwiching three birdies - gave the American a second-round 69 to leave him level with Donald on seven under and tied for 14th.
Donald, who revealed he has been suffering from a sinus infection, admitted he had been far from his best and would have to raise his game over the next two rounds.
"Sometimes you've got to fight ugly and play ugly," Donald said.
"It was very ugly today. It wasn't very good at all. Obviously it's not the hardest course in the world, but I didn't do many things well today.
"It's disappointing. But, again, sometimes you're going to have rounds like that. I remember at the BMW at Wentworth there was a round that was very similar. Didn't play very well. Kind of ground it out and kind of kept myself there or thereabouts, and hopefully I can do the same.
"I'm going to have to go pretty low on the weekend. Be nice to shoot a low one tomorrow, get in the mix, and make this one a bit fun for me and fun for everyone else."
