Jordan Spieth, Rory McIlroy, and other big names slid off the leaderboard at the weather-affected Abu Dhabi Championship on Friday, leaving American amateur Bryson DeChambeau to chase clubhouse leader Andy Sullivan in the second round.

After fog delayed the start of play by nearly three hours, Sullivan shot a second straight 5-under-par 67 to move clear on 10 under.

Spieth and McIlroy were in the marquee afternoon group, but both played erratically and were 1 over after 13 holes when play was suspended for the day because of darkness. Spieth was at 3 under and McIlroy at 5 under, with both struggling off the tee.

DeChambeau, the first-round leader following a 64, was a shot behind Sullivan after playing nine holes in 1 under. Starting on No. 10, he made birdies on two of his first three holes but bogeyed No. 18 in the fading light.

Joost Luiten (68) and Rafael Cabrera-Bello (67) were in the clubhouse at 7-under 137, with the leaderboard shorn of the leading players. Henrik Stenson dropped three shots in 12 holes before play was suspended to fall to 4 under overall, and Branden Grace was on the same score after shooting 74.

The European Tour said the third round will be a two-tee start.

Sullivan, one of the stars of the European Tour in 2015 with three victories, won three points from three matches for Europe in its big win over Asia in the EurAsia Cup in Malaysia last week. Clarke captained the Europeans for that event, a test run for the Ryder Cup, and has been further impressed by Sullivan’s play and attitude in Abu Dhabi — this time even closer up.

The 28-year-old Englishman started and finished his second round with three straight birdies.

‘‘Darren knows what I can do, so I don’t think it was imperative (to play well here),’’ Sullivan said, ‘‘but it bodes well when you do.’’

Clarke and Sullivan have been close friends since Sullivan turned professional in 2011 and the jokes have been flying between them this week.

‘‘He has completely taken the mick out of me for two days and I have told him that if he keeps this up, a pick (for the Ryder Cup) is out of the question,’’ Clarke said.

Sullivan, known for his big smile and easygoing attitude, says Clarke has been playfully abusing him for being a ‘‘short, fat guy’’ but has been giving it back.

‘‘He’s got 60 on his ball and, on the first tee, I said I didn’t realize you put your age on the ball,’’ Sullivan said, laughing. ‘‘I just try and have a bit of to-ing and fro-ing. It was good fun and kept it relaxed.’’

DeChambeau is the 2015 US Amateur and NCAA champion who plays with a home-made set of irons that are all the same length, explaining his self-styled nickname ‘‘The Golf Scientist.’’ He went out in the final group of the day, knowing he wouldn’t come close to completing his round, and made some ground back on Sullivan.

‘‘I had adrenaline going, that’s for sure,’’ DeChambeau said. ‘‘But there’s no anxiety, no nerves. Doesn’t matter what the outcome is.’’

The bogey on the par-5 18th came after a bad second shot out of a fairway bunker.

Spieth’s only birdie was on No. 10, and the American is two shots above the projected cut of 1 under. McIlroy made 12 pars and had a bogey on No. 9 after pushing his drive toward the rocks next to a lake.

PGA — Jason Dufner shot a 7-under 65, matching the best round of the first two days on the PGA West’s TPC Stadium Course and taking the lead in the CareerBuilder Challenge at La Quinta, Calif.

‘‘It’s a difficult golf course,’’ Dufner said. ‘‘There’s a little bit of room to play off the tee, but if you get off the path a little bit, you can get into some trouble. He’s got some water out there. He’s got some tricky bunkers. You get some uneven lies here and there. It’s definitely the most difficult of the courses we have played here.’’

Dufner (15-under 129) played the front nine in 6-under 30. He had only 22 putts, one-putting 11 of 12 greens in the middle of the round.

Jamie Lovemark was a stroke back after a 65 on the adjacent Nicklaus Tournament Course.

‘‘The greens are of kind of difficult,’’ Dufner said. ‘‘They run on some angles and there’s some slope.’’

Dufner was forced to lay up on all four par-5 holes and took advantage of many short approach shots.

‘‘Any time I'm inside of 130 yards I feel pretty good,’’ Dufner said. ‘‘I had some really good numbers with my wedges, which helps. I wasn’t in between on too many of them. I could go ahead and hit a full sand wedge or a full gap wedge a couple times.’’

Dufner’s drive on 16 perched on a ledge of dormant grass above one of the deep bunkers that line the left side. The ball at knee level, he slashed it 100 yards down the fairway before slipping to his hands and knees on the steep bank.

‘‘I was a little disappointed with that,’’ Dufner said. ‘‘I thought I would have a good go at that green in two and maybe get another birdie or possibly even an eagle and walked away with a five, but no damage done.’’

Dufner had a 15-under 129 total. Coming off a ninth-place tie last week in Honolulu in the Sony Open, he opened with a 64 on Thursday on the Nicklaus Course. He will play La Quinta on Saturday, and return to the Stadium Course for the final round Sunday.

Lovemark holed out from 105 yards for eagle on the par-4 first, his 10th hole of the day.

‘‘Got a little tired coming down the stretch,’’ Lovemark said. ‘‘There’s some long rounds out here.’’

Bill Haas, the winner in 2014 and 2015, was three strokes back along with Jason Gore, Anirban Lahiri, Andrew Loupe and Adam Hadwin. Haas shot 66, Gore 64, and Lahiri 68, all at the Nicklaus Course. Loupe had a 66 on the Stadium Course, and Hadwin a 66 at La Quinta.

Phil Mickelson was 11 under in his first start since in October and first since splitting with swing coach Butch Harmon to work with Andrew Getson. Mickelson had a 65 on the Nicklaus Course.

‘‘I'm probably a week away, if I'm being honest,’’ Mickelson said. ‘‘But I've also won with a lot less game than I have right now. I still expect to get in contention and have a good weekend, but a lot of iron shots are 12, 15 feet off.’’

The 2002 and 2004 champion is winless since the 2013 British Open.

Champions — Tom Watson bettered his age in the second round of the Mitsubishi Electric Championship in Kaupulehu-Kona, Hawaii, leaving him two strokes behind leader Duffy Waldorf.

The 66-year-old Tom Watson had a 7-under 65 at Hualalai Golf Course to move into a tie for fifth place. Waldorf also shot 65 to reach 12-under 132 and has a one-stroke lead over Tom Lehman (65), Davis Love III (67), and Tom Pernice Jr. (67) with one round left.