Imada also made a 50-foot birdie putt at the 16th as he picked up two shots in three holes to join Matteson at 13-under-par 203.
Both players had a 3-under 69 in Saturday's third round to extend their overnight lead from one shot to two.
Columbian star Camilo Villegas used a seven-foot birdie putt at No. 16 to pull within two strokes of the lead on the way to shooting a 4-under 68. He was alone in third place at 11-under 205.