Martina Hingis has booked her place in the final of the Chase Championships after beating her doubles partner Anna Kournikova in the semis.
Switzerland's world number one came into the match with a 10-1 lead from her previous 11 meetings with the Russian teenager, but Saturday's encounter was one of the hardest fought matches yet between the two friends.
Kournikova took an early lead, breaking Hingis in the seventh game. But the Swiss player broke back immediately. The next two games also went against serve, with Kournikova mixing a number of brilliant ground strokes with just as many unforced errors.
As the set wore into a tie-break, Kournikova's inconsistency combined with some strong service play from Hingis saw the world number one wrap up the set 7-6 (7-2).
Having come so close to taking the first set, Kournikova appeared to have lost her way as the second set got underway. Broken in the very first game, the Russian then had to defend a triple break point on her second service game to stay in any kind of contention.
It was Hingis who faltered next, double-faulting at break point on her own service to level the set at 2-2. But again Kournikova was unable to take advantage, losing her next two service games.
Hingis held her own serve to complete a 7-6, 6-2 victory.
The St Gallen player will now face Monica Seles in the WTA tour's traditional season-ender. The American completed a miserable day for Russian teenagers, beating Elena Dementieva 6-1, 7-6 in Saturday's other semi-final.
Sunday will see Hingis's fourth appearance in the final of the Chase Championships. After losing to Steffi Graf in 1996, the Swiss player won the tournament for the first time in 1998, beating Lindsay Davenport. Last year's final saw Davenport exact revenge.
swissinfo with agencies