Poor play or bad luck for Rafael Nadal?

NEW YORK -- After 2 a.m. on Saturday, less than an hour after he'd lost a Grand Slam match after leading by two sets for the first time in his career, Rafael Nadal entered the media interview room under Arthur Ashe Stadium. He had just finished a year without a major title for the first time since 2004 and faced tough questions about his future. But as far as he was concerned, he wasn't far from winning the match. He'd played well and lost anyway to a man playing better. All was not lost.

"I fighted until the last point all the time, good attitude," Nadal said. "Not enough to win today. I lost a couple matches this year like this."

He'd lost six matches like this in 2015 -- matches where he'd done enough to win in normal circumstances. Six times this year, he'd lost despite winning a higher percentage of return points than his opponent. Nadal has lost eight straight matches like this, where the winner has a lower winning percentage on return points. If these are lottery matches, Nadal has had a run of bad luck. And not once has he won despite winning a lower percentage of return points (0-9).

Going back to March 2014, it's a basic principle of tennis: Win more of your return points than your opponent does, and you'll have more chances to break serve. Break serve more than your opponent does, and you should win more sets -- and the match.

Sometimes, though, it doesn't work out that way. Sometimes you don't convert your break points, or you hold serve at love most of the time and then get broken in a close game. Or you win a couple of sets by a big margin and then lose three close ones.

For Nadal against Fabio Fognini, one culprit was break points. Nadal won 43 percent of return points to Fognini's 42 percent but managed to break on just 8 of 19 chances, compared to Fognini's 9 of 16.

Nadal's five other losses like this one in 2015 have all come on hard or grass courts, where the serve is more dominant and small margins make a big difference. Perhaps it's a sign of a failure of nerves, of an inability to play the best aggressive tennis in the biggest moments -- like when Fognini broke Nadal's serve at love at 4-4 in the fifth set with four winners.

But it's also probably bad luck, a concept Nadal can appreciate as an avid poker player. After all, before he lost eight straight lottery matches, he'd won six straight. Six times in a row when the winner won a lower percentage of return points, Nadal came out on top. That run of success coincided with his excellent 2013, when he won the French Open and US Open.

Nadal has won these kinds of close matches recently. There's no reason he can't recapture that luck -- or skill in the clutch, or whatever it was -- and turn around his losing streak in lottery matches.

Listen to Carl Bialik and Louisa Thomas discuss what's next for Rafael Nadal and count Serena Williams's comeback in Baseline, a podcast from the US Open.