We know that the number of break points a player saves in a given match can be a crucial statistic. But what about the number of game points he or she saves? The ability to break serve after your opponent has reached game point is a measure of a player’s stubbornness. Rafael Nadal and Maria Sharapova, two cussed competitors who are famous for never giving anything away, both have a knack for fighting through long, multi-deuce games to break their opponents’ serves—and, as often as not, their spirits.

Grigor Dimitrov is not known for this knack. No one has ever doubted the Bulgarian’s talent; it’s his toughness that has been questioned. But you couldn’t question it last week at the ATP Finals in London. During the early, round-robin portion of the event, Dimitrov showed off his varied arsenal of shots in a pair of runaway victories. Then, when the matches got tighter in the semis and final, he toughened up. On Saturday and Sunday, Dimitrov won two three-setters over two opponents who refused to go away easily, Jack Sock and David Goffin. The 26-year-old went 5-0 in his London debut, all against Top 10 opponents. His reward was the biggest title of his career.

In the final, it was Dimitrov’s ability to break Goffin’s serve when it appeared that Goffin was going to hold that made the difference. The first of these momentum-changing games came with the Belgian serving at 5-6 in the opening set. Dimitrov went up 15-40, only to see Goffin wipe away both set points with forehand winners; the second one elicited a rare show of frustration from Dimitrov’s coach, the mild-mannered Dani Vallverdu, who punched the tarp behind him. But Dimitrov himself didn’t get angry or lose heart; instead, he hung around and forced Goffin to keep serving, and keep hitting that forehand. Finally, on Dimitrov’s fifth set point, a weary-looking Goffin sent one into the net.

The scenario was much the same an hour or so later, when Goffin stepped to the line to serve at 2-3 in the third set. This time Goffin went up 30-0 on his serve, only to see Dimitrov come back to reach break point. After the two of them went back and forth for a few deuces, Dimitrov finally broke through when a Goffin backhand sailed wide. Again, it felt as if Dimitrov had outlasted his opponent mentally. When he went up 5-2, it felt like the victory was his.

As we know, though, old habits, and nervous habits, die hard. It would take Dimitrov five match points—three on Goffin’s serve and two on his own—to clinch the win. It would also take a little bit of luck. With a chance to get back to deuce on Dimitrov’s serve at 3-5, Goffin flipped an easy drop volley into the net that would have won him the point. Dimitrov, a 7-5, 4-6, 6-3 winner, fell face-first to the court, and stayed there.

The man once known as Baby Federer had waited a long time to win a title this big. He had weathered 10 aces and 37 winners (against just 20 winners of his own) from Goffin. And while he needed some help from his opponent to get across the finish line, well, that’s often what it takes to do something you’ve never done before.

“With the right set of mind, with the right people, with the right support, things happen,” said Dimitrov, who credited his success to the training “structure” that he and Vallverdu installed in 2017. It led to a season of firsts: His first Masters 1000 win, in Cincinnati; his first Australian Open semifinal; his first four-title season; his first ATP Finals victory in his first appearance; and his highest year-end ranking, No. 3.

“This makes me even more locked in, more excited about my work, and for what’s to come,” Dimitrov said. “It’s a great platform for me to build on for next year. It’s going to be amazing in the off-season. I know what I have to do in order to do good.”

I’ll hold off on any speculation about what we should expect from Dimitrov in 2018. He’s been saddled with a lot of expectations over the years, and now that he’s met a big one, he deserves a chance to savor the moment.

Next season, with Federer and Nadal leading the way, and Novak Djokovic, Andy Murray, and Stan Wawrinka returning, should be an explosive one for the ATP. Watching Dimitrov rip his running forehand, carved his slice backhand down the line, knife volleys away, and win the important points all week in London, it was obvious that there’s a place for his charismatic game at the top of the rankings, and in the late rounds at the Slams. Dimitrov has always added style to the sport; let’s hope he stays this stubborn in 2018.