Martin Flores and Patrick Rodgers were on eight-under while McIlroy, Phil Mickelson and Will MacKenzie were a further shot back, three off the lead going into the weekend.

McIlroy started on the back nine, where he made three birdies, and two more after the turn.

The last came after a fine bunker shot at the eighth hole and McIlroy told Sky Sports 4: "It's a real solid score, it sets me up well for the weekend.

"I wouldn't have minded picking up a couple more but I'm going to be in one of the final groups tomorrow and it should make for an exciting weekend."

Mickelson out-performed even McIlroy - his 66 was matched only by fellow American Steve Wheatcroft, who is four under for the tournament.

The left-hander's front nine featured four birdies and after a bogey at eight, he picked up three more shots on the way home.

"I played really well," he said. "I'd been turning 66s into 71s like yesterday and today it was nice to make such a good score."

Streb kept his momentum going with three birdies on the front nine and another at the par-three 13th, where he struck his tee-shot to within nine feet of the pin.

He would have kept the outright lead but for a tee-shot into the water at 16, where he dropped on the other side of the hazard and did well to scramble and lose only a single stroke.

"I scored pretty well, got it going for a few holes in the middle there and then hung on at the end," he said.

Streb already has a win to his name this season, at October's McGladrey Classic, and as he bids for a repeat he said: "I have the confidence, I know I can do it, but you've got to hit the shots over the weekend."