PGA Tour rookies Isaiah Salinda and Kevin Velo shot a 3-under 69 in alternate-shot play Friday to remain atop the leaderboard in the Zurich Classic, and leave defending champions Rory McIlroy and Shane Lowry six strokes back.

But their precarious one-shot lead feels anything but safe. Behind them, lurks an army of contenders, including the tandems of Ben Griffin and Andrew Novak at 16-under and the Hojgaard twins – Nicolai and Rasmus – at 15-under.