Was this the Rafael Nadal who won the Australian Open? The one who played with more conviction, and displayed more firepower, than ever before? The one who capped his Melbourne run with two exhilarating, and exhausting, five-set performances and proved that he is just as dangerous on hard courts as clay or grass? Gael Monfils, at least, is convinced.

“How about you?” a tired Monfils responded Tuesday night when asked about Nadal’s condition. “I think you have same eyes as me.”

Tuesday night there was too much for the human eye to see. There was Nadal, sprinting with abandon, stepping into the court, hitting his forehand deep and hard instead of spinning it short, and knifing volleys for winners. At times it was tennis that might be played on some other planet, where the pull of gravity isn’t as powerful and balls float, float and wait patiently for Nadal to clobber them. Since returning from a nine-week layoff because of knee tendonitis, the former world No. 1 had played some solid, but not great, tennis. On Tuesday, he was great. The knee pain, at least for now, has subsided, and his strained abdominal muscle, an injury sustained in Cincinnati, is holding up fine. When Nadal put Monfils away, he pumped his fists and danced a little longer than usual, especially for a fourth-round match. He was giddy, and for good reason.

“The knees are perfect,” he said. “Very important for me, no?  Gives me lot of confidence.”

Nadal’s confidence ought to make everyone else nervous. When the former No. 1 decides he’s playing at his best—like he did at last year’s Wimbledon and Beijing Olympics, and this year’s Australian Open—he’s the most difficult player on the tour to beat. Dare take a set off him, as Monfils did last night. It doesn’t matter to Nadal. He keeps punching, keeps playing at the same level for hour after hour, until his opponent wilts. Monfils, perhaps the least disciplined tennis player in the world, expended a lot of energy in the first set, most of it spent celebrating and riling up the crowd. As Nadal began the second set, he wasn’t concerned.

“If I play all the match like this, gonna be tough for him beat me,” he said he thought at the time.

While watching Nadal master Monfils, I was reminded of the Spaniard’s loss to David Ferrer here in 2007. Back then, Nadal didn’t have enough confidence to play aggressive tennis, at least not for four full sets. If a match became tight, he would revert to the style of his defensive-minded youth, spent on the clay courts of Majorca, and retreat behind the baseline. The new Nadal, the one who was the best player in the world for much of the last two years, doesn’t retreat. He takes more chances, charges the net more often, hits his forehand flatter and deeper, and makes better use of the down-the-line backhand. This is the Nadal who took Monfils out of the match last night—simply took the match away from him. Monfils continued to play, but not on his own terms. Nadal gave him no choice. This is the lesson that Andy Murray, who lost meekly this week, needs to learn, and quickly. To win majors on the faster surfaces, one must act more often than react.

Nadal has much work left in front of him, beginning Thursday, when he’ll play Fernando Gonzalez, who used his forehand and underrated serve to thwart the high-flying game of Jo-Wilfried Tsonga in the fourth round. Two years ago, Gonzalez pummeled Nadal at the Australian Open. Nadal has beaten him five straight times since then, including a routine fourth-round victory in Australia this year, and hasn’t lost a set. He’s had more trouble with Juan Martin del Potro, his likely semifinal opponent. The 6-foot-6 del Potro has beaten Nadal twice this year and plays the sort of game—in a word, punishing—that can turn matches into slugfests, rather than the physical and psychological battles that are more to Nadal’s liking. Nadal could have to overcome more than these opponents, too. If weather delays play, Nadal might have to play his quarterfinal, semifinal, and final matches on consecutive days (the U.S. Open is the only Grand Slam that schedules its semifinals and finals on consecutive days).

We all marveled at Nadal’s back-to-back five set miracles in Melbourne, where he had a day off between the semifinals and final. Let’s step back for a moment and say that Nadal manages to do something even more remarkable at this tournament. If he does, we’re left to contemplate one of the strangest moments in the history of tennis. At the top of the game, we’d have Roger Federer, certainly deserving of “Greatest of All Time” status and holder of 15 major titles, including the rare French Open-Wimbledon double. In second, though, we would have, in Nadal, the “Greatest Player Now.” Nadal, like Federer, would have at least one title at all four majors. Nadal, like Federer, would have a French Open-Wimbledon double to his name. Nadal, though, might have something else: He might have a victory over Federer in the final of all four majors, and a 6-2 overall record against Federer in major finals. Three more Nadal wins and the debate begins.

Tom Perrotta is a senior editor at TENNIS magazine. Follow him on Twitter.