You could almost say that in this, the season of Roger Federer’s discontent, Juan Martin del Potro has played the Great White Whale to Federer’s Captain Ahab in a re-enactment of that classic, Moby Dick.

Del Potro is big, fierce, and enigmantic, just like Herman Melville’s celebrated whale. Going into today’s quarterfinals in the Paris Masters, del Potro had mastered Federer in three consecutive matches—most recently less than a week ago, in the final of Basel, Federer’s hometown.

That one was a brutal war that went the (three-set) distance. But then so were the preceding five encounters between these two. That all started when Federer won their quarterfinal clash at the 2012 French Open in five sets.

Today, Federer finally harpooned his antagonist, winning 6-3, 4-6, 6-3. It was often a compelling affair, less because of how competitive it was (truth be told, Federer blew a good chance to wrap it up in straight sets) than because of the way Federer crafted his victory. He served superbly—converting 70 percent of his first serves, and won 81 percent of those points—used the full array of tools in his arsenal, and played with cat-like quickness reminiscent of his absolute best years.

Federer was on fire from the get-go, while del Potro looked sluggish and morose at the outset. But he had good reason, for Federer appeared to have his game figured out. Federer used his backhand slice often and judiciously; 47 percent of the backhands he hit in the first set were sliced. He put del Potro into awkward positions and opened up the court, enabling him to attack on a day when his reactions were crisp, sure, and confident.

Federer locked up the first break early, and swiftly held for 4-1. He was never in trouble on his serve early on, losing just three service points through a set and a third, while del Potro struggled to dig out those backspinners, forehand placements, and razor-sharp volleys.

But at about the middle of the second set, Federer seemed to fall back on that flat or overspun backhand, the one he shanks so frequently. Del Potro took full advantage of it. The games suddenly ceased flowing into Federer’s column so easily, and del Potro began to score punishing hits with that big forehand.

Still, neither man was able to break through the first nine games of the second, and Federer found himself serving to say in the set at 4-5. That’s when the wheels fell off, and that painful hesitancy that had marred his play these past few months reared its ugly head. At 30-all, Federer hit a third-shot, inside-in forehand wide of the line to give del Potro his first break point.

Federer fought off that chance with an inside-out forehand winner off a service return. But he made an unforced backhand error at deuce and smacked a tentative forehand into the net on break point to surrender the set. Significantly, only 17 percent of his backhands in the set were of the sliced variety.

Clearly distracted by that abrupt reversal of fortune, Federer continued to suffer into the third set; at one stage, del Potro won 14 of 19 points. But Federer managed to hold on and soon returned to the kind of game that had paid such great dividends earlier. He broke del Potro at 15 for 2-3, but the big man lashed back to take the next game. But Federer broke del Potro again in the seventh game, thanks to a slice backhand that goaded the Argentine into making a backhand error.

With that 4-3 lead in hand, Federer belted his way through the next game in a mere 86 seconds, and suddenly del Potro found himself serving to stay in the match. An aggressive attack and smash won Federer the first point, and del Potro’s resistance seemed to melt away. The only point he won in that final game was a service winner for 15-30, after which Federer converted his first match point when del Potro drove a forehand long to end an extended rally.