Matteson tied the low round of the year on the PGA Tour in shooting a bogey-free round of 10-under 61 to take the lead by three shots over Ricky Barnes.
Seven players are tied for third place at 6 under par, including three-time defending champion Steve Stricker. Stricker is joined by Garrigus, Scott Piercy, K.J. Choi, Brian Harman, Luke Guthrie and Gary Christian.
Of the 156 players in the field Thursday, 99 finished under par.