Spieth surprised by opening 67 after 'grind'

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Jordan Spieth was surprised he managed to shoot a three-under 67 to open the Tour Championship after grinding on Thursday.

The American endured a tricky day at East Lake Golf Club, but ended up mixing four birdies with just one bogey to be tied for sixth.

Spieth is still the projected FedEx Cup champion despite sitting three shots behind leader Kyle Stanley.

The three-time major champion said he had an inconsistent day, while lamenting missed opportunities on the back nine.

"I get done and look back and I'm surprised we're three under," Spieth said.

"I felt like it was really a grind out there and it's just because the first four, five holes of the round I was all over the place tee to green.

"My whole back nine I had a chance to birdie all but one of the holes and only made one of them.

"Things were off at different times and things were certainly on at different times that really pieced this round together and kind of helped what was an interesting day to still be in this golf tournament."

Joining Spieth in a tie for sixth was playing partner and US PGA Championship winner Justin Thomas.

Thomas is upbeat about his chances at the event, particularly after his efforts with the driver in the first round.

"It was a good day, it was a pretty easy day," he said. "I felt like all the birdies I made I hit it close, it's not like I made any long putts or anything.

"I drove it beautifully. That's probably the best round I've had driving the ball in a while, been working hard at it so it's nice to see the work has paid off.

"I feel like if I can keep driving it that well, I feel really confident."