Second-round birdie blitz has Piercy three shots clear

American Scott Piercy took a three-shot lead into the third round of the 3M Open in Minneapolis.

He birdied seven holes to card a seven-under 64 at the end of the second day at TPC Twin Cities.

Trailing him were Argentina's Emiliano Grillo and England's Callum Tarren after rounds of six-under 65 and eight-under 63.

Grillo collected five birdies and an eagle on the day while Tarren picked up eight birdies.

It boosted Tarren after a first round which ended with a single birdie and bogey.

Defending champion Cameron Champ only just made the cut on a round of three-under 68.