Tiger Woods’s return to golf after a month-long layoff fell apart, effectively, after just one swing Thursday. The sport’s brightest star began his first round at The Players Championship with a 3-wood at 8:08 a.m., and he immediately felt pain in his balky left knee.

Some 2 hours 20 minutes later, after he carded an unsightly 6-over-par 42 on the front nine, he shook hands with his playing partners, withdrew from the tournament, left TPC Sawgrass in a white Mercedes, and opened a seemingly bottomless box of questions about his fitness not just for next month’s U.S. Open, but for the rest of his career.

“I’m having a hard time walking,” Woods, 35, said afterward.

That much was apparent during a gruesome opening nine — his worst ever at TPC Sawgrass — in which Woods winced and limped around architect Pete Dye’s mound-laden layout. Woods’s left leg has already been surgically overhauled. He famously won the 2008 U.S. Open when it was broken, then missed the rest of that season after having that injury, as well as a torn anterior cruciate ligament, repaired. He has had four procedures on his left knee dating from his days as an amateur.

Now, even with a new swing designed, in part, to put less pressure on his left leg, he continues to have problems. He originally suffered a grade one sprain to his medial collateral ligament and a mild strain to his left Achilles’ tendon in the third round of the Masters, when he awkwardly hit a shot off pine straw at Augusta National’s 17th hole. He hadn’t played a competitive round since — rather, he had spent some time in a walking boot — and only started practicing again Monday. Then came that first swing in competition, and the snowball began rolling downhill.

“The knee acted up, and then the Achilles’ followed after that, and then the calf started cramping up,” Woods said. “Everything started getting tight, so it’s just a whole chain reaction.”

Similarly, Woods’s every move creates a chain reaction throughout golf. The PGA Tour’s flagship event — led after the first round by Nick Watney, who managed an 8-under 64 despite a double bogey and leads by one over Lucas Glover and two over 54-year-old Mark O’Meara — is now overshadowed not by Woods’s presence, but by his absence. He withdrew here last year with 12 holes to play in the final round because of a neck problem.

Now, with the U.S. Open at at Congressional Country Club in Bethesda only five weeks away, comes a murkier outlook. In an interview Tuesday, Woods said his injuries — which caused him to pull out of last week’s event in Charlotte before it began — wouldn’t affect his appearance at Congressional.

“I’m going to be there,” he said.

Even his friends can’t get a read on his situation. O’Meara, long close to Woods, played practice rounds with him Tuesday and Wednesday and dined with him Wednesday night, but said he was “shocked” at Woods’s withdrawal.

“Obviously, it’s pretty bad,” O’Meara said. “He needs to get that fixed, because I know how much he loves the game, and I know how badly he wants to be competing — and the game needs him.”

Now, Woods can’t say what might come next. “Give me a few days to see what the docs say, and we’ll take a look at it,” he said Thursday. But experts in orthopedics said Woods’s history of problems — and the repetitive, stressful motion of the golf swing — can lead to chronic issues.

“There can be a cumulative effect of multiple injuries, leading to multiple surgeries, with wear and tear,” said Ronald Navarro, an orthopedic surgeon who regularly repairs torn ACLs. Navarro, who has never worked with Woods, said repeated surgeries to remove menisci, pads of cartilage which help protect the knee joint, can lead to the early stages of arthritis. Once removed, menisci do not regenerate.

“We’ve watched Tiger age so rapidly right before our eyes,” said Brandel Chamblee, a former tour pro who’s now an analyst for the Golf Channel. “It’s really sad to see . . . where this phenomenal athlete is now, in a sense, kind of an old man out there.”

Indeed, Woods hit his tee shots Thursday, then carried the club in his left hand as he made his way down the fairway, all but using it as a cane. He lagged well behind his playing partners, Matt Kuchar and Martin Kaymer.

“Tiger looked like he was in pain today,” Kuchar said. “You could tell he was walking quite slowly, quite gingerly.”

He opened by surprisingly feeling pain on that opening tee shot. He had to hit his second shot with his stance in pine straw, and slipped a bit, further aggravating the injuries. He opened with a bogey, but looked worst at the par-4 fourth, where he yanked his drive well left. He cursed himself in the tee box, then chunked his approach into the water. After he dropped, he inexplicably hit his pitch — to a pin at the back of the green — well short, and it bounced back into the water.

“Those were just awful,” he said, and he needed an 18-foot putt there to save triple-bogey 7. The end result: He finished one shot off the worst nine he has ever played on the PGA Tour.

So now what? Woods hasn’t won anything since November 2009, and his last major championship victory — that 2008 U.S. Open — came after he played against the advice of doctors. He said he had medical permission to play here, though “the more rest I get, the better it would be, obviously.”

Thursday, as he drove away from TPC Sawgrass almost before the tournament had started, there was no telling how much rest he would get.