Thursday’s Northern Trust first round for Jordan Spieth was a bit of a show-me moment — for himself. After posting two rounds in the 60s at the Wyndham Championship last week, Spieth stunned himself with a third-round 77 that left him missing the Saturday cut.

He shot a 4-under-par 67 Thursday.

“For me, I came in honestly off of Saturday last week searching a bit, and really thinking about just playing some solid golf to make sure I get two chances at trying to work my way into contention and hopefully make it to East Lake [for the Tour Championship],’’ Spieth said. “I mean, that’s the ultimate goal for me. If I were to make it to East Lake at this point, it means I play some really solid golf these next two weeks.’’

Asked what he was searching for entering this week, Spieth said, “I just had a little doubt in what I was working on, and I hit quite a few balls out of play. Saturday was just a fluke day that would have happened whether I was No. 1 in the world or not. Everybody has those random days once, twice a year where you wanted to forget them. I just owed it to that and put me in a better frame of mind.’’

Aaron Baddeley, after going 2-over par through four holes, withdrew from the tournament Thursday with a back injury, ending his FedExCup Playoffs.

He said he will return to competition soon with hopes of becoming a captain’s pick for the Presidents Cup at Royal Melbourne in December.

Baddeley, who hadn’t played in the six weeks leading up to this week because of a back injury, was ranked 112th on the FedExCup standings.

His withdrawal means he cannot advance to next week’s BMW Championship.

“It felt like I would only make it worse, so it’s best not to play,” Baddeley said. “The injury feels like it has healed, but the sides of my back still feel really tight.’’

Reigning British Open champion Shane Lowry, playing in his first tournament since Royal Portrush, shot a 2-under-par 69. Reigning U.S. Open champion Gary Woodland, who has struggled since his win at Pebble Beach, shot a 2-over 73.

Phil Mickelson, who has struggled with his game in recent months, shot a 1-over 72.