Novak Djokovic moved ahead for the first time in his long-running rivalry with Rafael Nadal when the world number one thrashed the Spaniard to win the Qatar Open in Doha on Saturday.
Djokovic has cruised to his spot in the final round, beating Dustin Brown, Fernando Verdasco, Leonardo Mayer, and Tomas Berdych.
Nadal will next take on 94th-ranked Ukrainian Illya Marchenko, who upset Spain's David Ferrer in the first round and continued his surprise run this week by taking out France's Jeremy Chardy 6-3, 7-6 (7-3) on Thursday.
Djokovic took the next two games as well to secure his first ever semi-final appearance at the Qatar Open. Nadal has not won a set in their last four matches, even at his former strongholds, Roland Garros and Monte Carlo. So it does definitely give me a great deal of confidence for the rest of the season.
Djokovic is preparing to defend his Australian Open title from 18 January. "Since I know this sport, I never saw somebody playing at this level", Nadal said. Djokovic grabbed the 2-0 lead on the back of his eighth point in the last 10 played.
Prediction: Djokovic in straight sets.
The Serb, who had beaten Berdych in 21 of their previous 23 encounters, lost his very first serve and then faced another break point to go 1-4 down.
Nadal fell to 67-32 in career finals.
"I played against a player who did everything flawless", Nadal said. "It appears time to time, but it's nothing that really is major that I will be concerned about".
He also fired down six aces and hit 16 winners.
"I know I'm capable of winning many matches so if I can reach the third or fourth round in Australia I'd be very happy".
The Swiss dropped just two points on serve through the first set, but Federer showed signs of fatigue in the second.
Their most recent meeting at a Grand Slam was at the quarter-finals of the 2015 French Open - on Nadal's favourite surface, clay, with eventual finalist Novak Djokovic going down to Stan Wawrinka and seeing his dreams of a calendar slam that year cut short by the Swiss.
He wrapped up the match after 73 minutes, striking a total 30 winners to just 13 unforced errors.
Djokovic won the next game to go 5-1 up.
Djokovic admitted: "Every time we play, there is a lot at stake, it is always a great challenge".