James Hahn struck a six-under-par 65 to sit at the top of the leaderboard at the midway point of the Waste Management Phoenix Open in Arizona.
Hahn registered six birdies in a blemish-free round which sees him lead on 10 under after two rounds in the desert.
The American replaces Rickie Fowler at the summit after the world number four carded a 68 to advance to nine under, striking four birdies and a solitary bogey.
Fowler is joined on nine under by Australian Danny Lee, whose seven birdies and two bogeys saw him sign off on a 66.
Fellow first-round leaders Hideki Matsuyama and Shane Lowry slipped back to tied third after they both struck 70.
England's Ian Poulter and two-time major champions Padraig Harrington are both certain to miss the cut at four-over, though play was suspended due to bad light with a number of players' rounds incomplete.
There was a nice moment for rookie Jack Maguire, who struck a hole in one on the par-3 12th, but he still finished on 12 over, with the damage done after yesterday's 83.
Source: PA
