Englishmen Lee Westwood and Justin Rose are both in contention just three shots off the pace at the halfway stage of the Honda Classic at Palm Beach Gardens in Florida.
Rose added a four-under-par 66 to his opening 68 to get to six-under-par, while Westwood's 68 on Friday kept him in the chasing pack, three shots behind leader Luke Guthrie.
Rose started fast with birdies at the first three holes, although he was able to add just one more - at the 12th - in a bogey-free round.
Westwood had three birdies and a solitary bogey at 15 as he chases his first victory on the PGA Tour since 2010 and his third in all.
Former US Open champion Graeme McDowell is a shot behind the six-man log-jam at six-under after his round of 68.
But the man to catch on the weekend is Guthrie, who shot a seven-birdie 63 in a bogey-free round. The 23-year-old from Illinois is in just his second year as a professional and has just one top-10 finish to his name on the PGA Tour.
He is a shot clear of fellow American Michael Thompson, who had a second round 65, with former Ryder Cup player Boo Weekley a shot further back after his 67 got him to seven-under.
Canadian Graham DeLaet also got it to seven-under after two birdies in his last five holes.