It was only fitting that Jordan Spieth's final frustration in a week and a season loaded with them took place in the muck at water-logged Aronimink Golf Club on Monday.

All through the 2018 BMW Championship, all through what by his standards has been a lost season, Spieth has been stuck in the mud, mired in a run of erratic golf that nothing in his brief but impressive history foretold.

Though he earned nearly $3 million in 2018, there were no wins in majors. There were, for a first time in his six Tour seasons, no wins at all. No runner-up finishes, either. Whenever he seemed poised to rebound, there would be a deadly three-putt, a double-bogey, a contention-killing round.

Spieth finished tied for 55th at Aronimink, his three-over, final round 73 not only costing him a spot in the season-ending Tour Championship but likely earning himself a PGA Tour punishment thanks to an arcane, two-year-old rule.

Only the top 30 in the FedEx Cup rankings advance to Atlanta in two weeks. Spieth finished 31st. When he plays in the Ryder Cup later this month. it will count as his 24th PGA event this season.

The Strength of Field Regulation mandates that players without a lifetime exemption must play in 25. If not, they must add a new tournament to their schedule. Spieth did neither.

Tour officials haven't officially commented on what would be a first violation. If they do impose a penalty on Spieth, one of the game's top attractions, it could range from a $20,0000 fine to a three-tournament suspension.

"I'd talked with the Tour a little while back and I didn't really think much of it," Spieth told reporters after his round ."But if it becomes a situation, then I'll obviously accept whatever fine it is. I'll go on and try to add one [tournament] every year, but it's kind of tough."

All that could have been avoided if Spieth, who came here on the FedEx bubble at 27, had played as well on the defenseless course as most of the other 68 competitors.

Though he finished 12th at the Dell Technologies Championship last week, Spieth saw some promise in a game that has sputtered since his 2017 British Open win. He arrived in Newtown Square hopeful his putting and driving woes were behind him

"I was in control of my own destiny and I just didn't have it this week," he said. "I was riding some momentum. But all in all my game just kind of got a little off."

The suddenly erratic Spieth ended the tournament 47th out of 69 in greens-in-regulation, 49th in driving accuracy, and 59th in strokes gained putting.

A late birdie run salvaged an opening-round 67. But a one-over 71 on Friday – a day when there were a pair of 62s and an average score of 67 — sank him.

"That second round, you can't shoot over par out here," Spieth said. "That just threw me so far back."

After a 66 on a gloomy Saturday, he was still ranked at 31. He needed a superb round to get to Atlanta and a bad one from players just inside the top 30, including Keegan Bradley, who instead shot a 64 to win the BMW.

"I knew that if I could shoot four or five under in tough conditions that it would make a little bit of a difference," Spieth said. "I came out trying to go low, but I knew it was in other's people's [hands]."

So Spieth, who wore a bandage on a sore wrist, will be off the next two weeks then head to the Ryder Cup in Paris, where he'll once again hope his game is reborn.

"I'm not that far off," he said earlier. "I'm really not."