In the wake of the Spurs’ playoff series-clinching, 114-75 rout of the Rockets on Thursday, it was hard to know which was more shocking: that San Antonio could play so well without Kawhi Leonard and Tony Parker, or that James Harden could play so poorly. The Houston star scored just 10 points on 2-of-11 shooting in more than 36 minutes of play, looking nothing like a leading contender for NBA MVP honors.

Harden’s Game 6 flop — on his home court, no less — was such a head-scratcher that it had some observers considering an intriguing possibility. What if he had been playing with the aftereffects of a concussion he suffered late in Game 5?

That was a question being posed by The Ringer’s Bill Simmons, among others. There has been no indication from the Rockets that Harden had suffered a brain injury in Tuesday’s overtime loss to the Spurs, but he did fall to the court after taking an elbow to the head from San Antonio big man Pau Gasol, and it could explain his struggles at the end of Game 5 and throughout a desultory Game 6.

If Harden did have a head injury, it didn’t stop him from hitting the club after Thursday night’s game. TMZ has video of him partying at Set in Houston and reports that he followed that up with a trip to a strip club.

In Game 5, it appeared that the Rockets were set for a crucial win at San Antonio when Leonard, an MVP candidate in his own right, was forced to leave with an ankle injury. However, Harden not only failed to take advantage of the absence of the league’s best perimeter defender, he was stunningly ineffective in the final four minutes of regulation and through the five-minute overtime period.

In that span (per Fox Sports), Harden scored four points on 1-of-6 shooting, turned the ball over four times, and committed two costly fouls, including an offensive foul on what could have been a game-winning possession with seconds left in regulation. As that 110-107 Spurs win unfolded, some wondered about the possibility that the five-time all-star had suffered a concussion.

On a Ringer podcast after Game 5, Simmons said “I really hope Harden had his bell rung, or something, because he was just [terrible].” As of this writing, the Rockets had not responded to a request for comment.

After Thursday’s game, ESPN’s Stephen A. Smith expressed complete befuddlement with Harden’s performance, saying, “I think there needs to be an investigation, to be quite honest with you. He looked like he was drugged out there, for crying out loud. Literally comatose.”

“Somebody might have slipped something into his drink,” Smith said of Harden. “Somebody might have done something to him. I have no clue. But that is not James Harden that showed up for the Houston Rockets tonight. Somebody with his jersey showed up. It wasn’t him. I cannot believe what I saw.”

In any event, Game 6 marked an ignominious end to what had been a majestic season for Harden. He took his playmaking abilities to new heights, leading the NBA with 11.2 assists per game while finishing second in points (29.1). He also led the league in win shares (per Basketball Reference), while taking a Rockets squad for which little was expected to the third-best record in the NBA.

In fact, taking into account that Harden became the first player in NBA history to total 2,000 points, 900 assists, and 600 rebounds in a single season, and that he was the first to both score and assist on 2,000 points in a season, some argued that he submitted the greatest offensive campaign in league history.

In time, those accomplishments will return to the forefront, as memories of the Thursday’s debacle recede. Meanwhile, though, many have been left wondering if Harden finished his season in full possession of his faculties.