Rafael Nadal knew something had to change.

It was nearing midnight in Australia on Friday, and his match against Karen Khachanov of Russia was heading into its third hour. Nadal still had a comfortable lead, but the 25-year-old Khachanov was gaining strength and closing in on the third set. Nadal, a decade older, and just back from a nearly six-month rehabilitation from a chronic foot injury, needed to do whatever he could to avoid one of his classic battles of attrition. Nadal has often won those battles, and could still, but possibly at a significant cost.

At this point in Nadal’s career, how he might win is as important as winning itself.

And so for the final moments of the third set and then to start the fourth, Nadal crept a few steps closer to the baseline. He aimed his serves at the lines, and every time he saw a glimmer of an opening he went for it, instead of relying on his signature strategy of hitting eight shots to set up a winner on the ninth.

“If I am able to have the break back, fantastic,” Nadal said later, describing his return to the strategy that had allowed him to gain the early upper hand on Khachanov. “If not, on the fourth I’m going to start playing more aggressive again. Let’s see if it works.”

The results of the experiment came fast, with Nadal breaking Khachanov’s serve in the second game of the fourth set. Nadal blasted a service return for a winner, smacked an untouchable, cross-court forehand from what is supposed to be the backhand corner of the court for him, then sealed the break with a running backhand up the line. Then he crouched and pumped his fist four times, the finish line now just four games away.

“You need to be quick on making the right decisions,” he said.

There has always been an urgency to Nadal’s game. He ends every changeover with a sprint back onto the court. But what has become apparent for him and his aging contemporaries in Australia over the past week is how important taking care of business on the court quickly has become.

Nadal, who said he could barely play for more than a half-hour without his foot causing him pain just six weeks ago, has won nine of 10 sets in three matches at the Australian Open. In his warm-up tournament, he won all six of the sets he played in three matches on his way to the title.

Gaël Monfils, the 35-year-old Frenchman now playing some of the best tennis of his career, is on a similar efficiency tear. Monfils has not dropped a set in three matches and also won a tuneup event in Australia earlier this month.

He came awfully close to losing a set Friday afternoon against Cristian Garin of Chile, who had what appeared to be a commanding 4-1 lead in the first-set tiebreaker. But then Monfils found a way to do his Monfils thing, throwing those long arms and legs and his lusty movement into every shot. A few big serves and then a perfect backhand down the line gave Monfils the set and from there he was in cruise control, chattering with his wife, Elina Svitolina, who had lost earlier in the day, as she watched from the stands.

“Very lucky and fortunate to win this breaker, and I just think I was solid enough to win in straight sets,” Monfils said.

Monfils, who faces Miromir Kecmanovic of Serbia in the fourth round, and Nadal, who will play Adrian Mannarino of France, do not have to look far for the cautionary tale.

The week did not work out the way Andy Murray had wanted or hoped or thought it would, especially after his travels to Australia started on such a high note.

Last week, as Novak Djokovic sucked up most of the tennis oxygen, Murray stormed under the radar into the final of a tuneup tournament in Sydney, with wins over the much higher-ranked David Goffin, Reilly Opelka, and Nikoloz Basilashvili. He dropped the final to Aslan Karatsev, but that seemed almost beside the point.

Murray’s forever comeback from hip resurfacing surgery seemed to be rounding into form, especially after he prevailed in his first round match over Basilashvili, a five-set marathon that thrilled but also likely doomed the rest of the tournament for Murray. Murray smothered Basilashvili, the hard-hitting and freewheeling Georgian, in the first set and looked like he was going to have a short afternoon. There he was, defending in the corners, landing flashy angled winners and displaying the creative arsenal that made him the world’s top player five years ago.

But three hours later he was still battling, and after the win, he spoke like a player who understood well that success on the court now was as much about how he wins as it is about whether he wins.

Murray said he has been talking about this with his team for some time, which makes sense. His Grand Slam appearances since the start of the pandemic have included either an epic win followed by a quick loss or just a loss in an epic.

Murray and his crew have batted around the idea of playing more aggressively, trying to end points more quickly with more aggressive shots. But that, he said, carries the risk of losing more games, resulting in longer matches, especially now, when he is playing what he characterized as “top 20 level tennis,” as opposed to top five or top two. They decided the fastest route to victories is to play better rather than different.

“Playing my game style but playing it at a higher level,” he said. “When I look back at a lot of my matches in like 2015, 2016, like I was quite sort of efficient and clinical, like when I had opportunities and when I was, you know, ahead of guys, I’d finish them off quickly.”

The price for not finishing them off is plain. Two days after the marathon win against Basilashvili, Murray came out flat and allowed Taro Daniel of Japan, a 28-year-old journeyman ranked 120th, who has never been ranked higher than 64th, to dispatch him in three sets. Murray could not recall ever losing in a Grand Slam to someone ranked outside the top 100.

“Really disappointed,” he said of a result that had him questioning whether he would play another Australian Open, especially if his results at Grand Slams do not improve. “Making second rounds of slams is not something I find particularly motivating.”

Murray, of course, would like once more to be playing in the second week of the most important tournaments, something Nadal did not realize was going to be possible this quickly, and at a time when figuring out how to win quickly has never been more important, with Friday’s win serving as the latest evidence.

“I made the right decisions,” he said.