Daniil Medvedev is one match away from successfully defending his title at the Nitto ATP Finals.

Medvedev came through three tough matches in the group stages but found progress a lot more smooth against debutant Casper Ruud in the semi-finals.

The young Norwegian battled to victory against Andrey Rublev on Friday to book his spot in the last four but second seed Medvedev was far too solid, the Russian winning 6-4 6-2.

Medvedev started strongly, breaking early to take a 2-1 lead in the first set and dictating play from the back of the court as Ruud struggled to contend with his opponent's deep groundstrokes.

The Russian won 85% of his first-serve points as he wrapped up the opener in 42 minutes.

The second set followed a similar pattern to the first, with Medvedev racing into a 4-2 lead before closing out the match in 80 minutes, sending down 17 winners and making just 14 unforced errors in the one-sided victory.

The match marked world number two Medvedev's ninth win in a row at the ATP Finals and he improved his head-to-head record over Ruud to 3-0.

Medvedev will take on either Novak Djokovic or Alexander Zverev in the final on Sunday.