Jordan Spieth first contended in a PGA Tour event in 2010. He was 16, and opened the Byron Nelson Classic, a tournament played on his home course, with three straight rounds in the 60s. He has not yet turned 20, and yet of the names and faces at Congressional Country Club for this week’s AT&T National, he counts as prominent because he has so much promise.

Spieth, though, doesn’t see any of it as pressure.

“I just need to sit back and say, ‘Who cares?’” he said Friday afternoon. “It’s just a round of golf.”

Spieth’s second round of the AT&T National, played on a still-stout Blue Course at Congressional, was all but perfect: five birdies, no bogeys, a 66 that got him to 7-under 135 at the tournament’s midway point, tied for the lead with Roberto Castro after the completion of the Friday morning rounds. Play was suspended at 2:44 p.m. because of lightning in the area, and even with a chunk of the field still on the course, Castro and Spieth still held the lead.

Spieth’s presence at the top of the leaderboard could spice up a tournament that could use a jolt. Tiger Woods hosts this event, but his withdrawal because of an elbow injury has been palpable over the first two days. Though the crowds picked up Friday afternoon, attendance is clearly down from last year, when Woods won the second of his two AT&T National titles.

So introducing Spieth: The golf world first heard of him at the Byron Nelson three years ago, when he tied for 16th, and he played a year at the University of Texas before turning pro. But when he did so, he had no status on the or PGA Tours, so he figured he might not know where he was playing from week to week, his ability to get into tournaments based on performance and sponsor’s exemptions.

But in early March, he finished second in a PGA Tour event in Puerto Rico, and followed it with a tie for seventh in Tampa. He now has four top-10 finishes, and that string of performances has him in position to play PGA Tour events for the remainder of this season-- excluding the FedEx Cup playoffs, unless he wins a tournament — and next season.

“I think it’s a great position to be in,” Spieth said. “I’m just free-swinging. I can’t be in the playoffs unless I win, and that makes winning the No. 1 goal.”

This would be an impressive place to achieve that goal, and Spieth looks prepared. He hit all 18 greens Friday despite the thick rough and a course that stretches to 7,569 yards. He buried a 25-footer for birdie on the first, and that got him rolling.

Castro, too, handled himself well. After opening with a 66 Thursday that gave him a two-shot lead, he made an early bogey at the third Friday, but responded with birdies at 8, 9 and 16 — and no more bogeys — to shoot 69 and remain tied with Spieth.

“It feels good to play two rounds under par,” Castro said. “It’s a very hard golf course.”

D.H. Lee of South Korea also shot 66 Friday morning and sits two back of Spieth and Castro at 5-under 137. Cameron Tringale and James Driscoll, a University of Virginia product, are in at 4-under 138.

The cut — the top 60 players and ties play the weekend — will come upon completion of play Friday.

Among those in danger of missing the cut, which is currently projected at 2 over but could move to 3 over: K.J. Choi, the 2007 AT&T National champ who shot 76 Friday and is 4 over; Hunter Mahan, the 2009 runner-up here whose 72 Friday left him 5 over; and last year’s runner-up Bo Van Pelt, who opened with 79 Thursday and needs a solid round Friday afternoon to earn a spot for the weekend.

Masters champ Adam Scott shot an even-par 71 and is 2 over, likely ensuring his spot for the weekend.