Taylor Fritz fended off Alexander Zverev 6-3, 3-6, 7-6(3) to become the first American since James Blake in 2006 to reach the ATP Finals final.
Ruud secured his spot by taking the opening set against Rublev.
Swiatek and Magda Linette led Poland to a milestone win in Malaga.
No. 2 Alexander Zverev stopped No. 4 Carlos Alcaraz 7-6(5), 6-4 to score his eighth straight win and book his spot in the ATP Finals semifinals.
Sinner has now won eight of his last nine against Medvedev.
Taylor Fritz moved closer to a second straight ATP Finals semifinal with a 5-7, 6-4, 6-3 comeback conquest of Alex de Minaur in Turin today.
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