TURIN, ITALY (REUTERS) - Defending ATP Finals champion Daniil Medvedev stormed into the final of the season-ending tournament on Saturday (Nov 20) after crushing Norway's Casper Ruud 6-4 6-2.

Russian Medvedev will face either Novak Djokovic or Germany's Alexander Zverev in Sunday's final.

Medvedev started strongly against Ruud, 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 per cent 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 25-year-old US Open champion said one key to success was to never let up regardless of what the scoreboard says.

"As soon as you are a set and a break up you feel like you are in control, but that is when the danger is," Medvedev said.

"You need to stay focused and fight for every point. In the last game I had 0-30 on my serve and, until the last point, it is never over. So I am happy I was able to finish it."

Medvedev cruised through the round-robin stage of the season-ending tournament with wins over Hubert Hurkacz, Alexander Zverev and Jannik Sinner before dispatching Ruud.

"I think all the matches were a great level. Different opponents and different styles," he said.

"I managed to win all the matches. It was not an easy match (today). When you are in the final you can't complain, so I am just looking forward to tomorrow and hopefully I can have my best match."

The result 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 is 4-6 lifetime against Djokovic, including his straight-sets win in the final at Flushing Meadows this year, and 6-5 against Zverev, having won the last five straight.