INDIAN WELLS, CA, USA - The future of the sport and one of its greatest champions collided in a fascinating clash as a young Serena Williams faced off against Grand Slam champion Stefanie Graf in the 1999 Indian Wells final.

Twenty years ago on March 13, 1999, the last two players standing at Indian Wells put on display a crossover between two of the greatest careers tennis has ever seen - one a few months from its culmination, the other just getting started.

At the time, 17-year-old Serena was a newer face on the WTA Tour, chipping away at her ranking and collecting her first Top 10 wins and late-round appearances. With the spotlight on older sister Venus Williams, Serena was coming into her own under the radar and eventually claimed her first WTA title in head-turning fashion at Open Gaz de France in February 1999 (see video below).  

Read more: Remembering Serena Williams' first WTA title

Graf herself was very aware of the firepower that the young American possessed: the pair had already measured up against each other once previously. Graf won that one, escaping in three close sets to advance in Sydney earlier in the year.

Serena’s strength was her aggressive game, according to Graf, then ranked World No.7, but her inexperience at the big stages could be a major weakness.

“I think [Serena] is somebody that has a lot of shots,” Graf had told press in Indian Wells. “I think she's been lately starting to go a little bit more for her shots. I think she has a lot of strengths, same as Venus, especially on her serve. She can obviously put you under pressure pretty early on. She has got a very good return.

“I kind of thought, you know, she has a lot of potential. I think it's for her to figure out what kind of game she wants to go ahead with. I mean, I think she hasn't so much so far a totally clear mind on it. Sometimes she's coming in on the wrong shots.

“She's trying right now to do different things. It's going to take time for her to choose the right shots at the right time.”

Indeed, the 1999 Indian Wells final was a perfect example of experience versus youth as 17-year-old Serena - fresh off of winning her first WTA title - took the court against 29-year-old Graf, who owned 106 WTA titles and 21 Grand Slams.  

But Serena was coming in on a hot streak, her maiden win in Paris galvanizing her and giving her the confidence to face up against the game’s biggest stars.

“It was really good for me to win that tournament last week because I really was able to see that I can go out there and I can win,” Serena said at an Indian Wells press conference. “I don't know. I really practiced really hard since the end of last year and the beginning of this year, I was really practicing hard and really focused. My hard work is beginning to pay off.”

Serena’s hard work and steady climb up the ranks were something that the tennis world - especially American tennis fans - had been eagerly awaiting, according to Indian Wells Assistant Tournament Director Peggy Michel.  

Michel joined the Indian Wells team in 1985, and she recalled the growing buzz as the 17-year-old tore through the draw. “Everybody was just so excited because Serena was something brand new, her and Venus were like a fresh of fresh air,” she said.

“And she was American, and always we’re looking for who we’re going to pass the torch onto. Who will continue for the United States? Are they going to be ready for a changing of the guard? It’s always very important that we had somebody waiting in the wings that is going to come on when Lindsay [Davenport] and the other girls decide to retire.”

So it was almost symbolic that, en route to the final against Graf, Serena took down the then-World No.2 Davenport in a second-round stunner, winning 6-4, 6-2. In fact, she scored four Top 20 wins in the same event - a career-first for Serena.

She kept that momentum going in the final against Graf and took the first set, 6-3. But Graf responded like a Grand Slam champion, and stormed back to take the second set and power ahead to a 4-2 lead in the third.

Serena rallied to make it 4-4, and with Graf serving at 6-5, bidding to take it into a tiebreaker Serena summoned up all of her power to apply pressure against the German. Finally, Graf’s famous forehand let her down, and Serena edged through to triumph 6-3, 3-6, 7-5 for the biggest title of her career.

While both players employed an aggressive power game, Serena’s 35 winners far outpaced Graf’s 11.

“It means a lot to me because Steffi is a great champion,” Serena said after the victory. “She has more titles, from what I hear, than any man or lady playing tennis. It's very exciting for me to be able to have this win.

“This is the biggest tournament I ever won. I know that I can win the big ones now. I don't know how many matches I've won in a row, but it's enough to win a Slam. It's seven in a row to win a Slam. I'm prepared to do that.”

“The big ones” weren’t too far away for Serena, who would go on to end the year by lifting one of the biggest trophies of all: her first Grand Slam at the US Open. The first of the Williams sisters to achieve the feat, Serena emphatically cemented her position at the helm of a new wave of young tennis stars ready to make their mark.

By contrast, Graf would also finish the year with a Grand Slam title at the French Open and a run to the Wimbledon final, before calling time on her career. “I didn't feel like going to another tournament,” she admitted at her US Open retirement announcement.

With her career haul of 22 Grand Slam singles wins, the German left behind a seemingly untouchable Open Era record as a part of her legacy of dominance.

But Serena would eventually surpass her in this as well, claiming 23 Grand Slam titles of her own just 18 years later.

In photos: 23 and counting - Serena's singles Slam wins 

“Of course, you had to feel for the Steffi Grafs and the Lindsay Davenports, because you had watched them do the same thing: we watched them come up in the rankings, and then they started to dominate,” Michel said.

“And then, as with all champions, there’s going to be a period where they might lose a step. They might not hit as hard. And then that next generation comes through.”