Oct 31 (Reuters) - Novak Djokovic has signed up for both singles and doubles duty at next week"s Paris Masters, as the Serbian world number one returns to competitive action for the first time since his defeat in the U.S. Open final to Russian Daniil Medvedev. Djokovic, who is level with Roger Federer and Rafa Nadal on 20 major titles, has not played since coming up short last month in his bid for a calendar Grand Slam, losing in straight sets to Medvedev at Flushing Meadows. The 34-year-old will be the top seed at the Masters 1000 event in Bercy, where he is a five-time champion, and will also team up with countryman Filip Krajinovic with an eye on some practice ahead of the Davis Cup at the end of November. "He"s going to play with Krajinovic, his buddy from the Davis Cup," tournament director Guy Forget told reporters on Saturday. "He said he would commit himself to play for the Davis Cup for his own country. This is why he wanted to play doubles here. "We don"t often see him play doubles, so we"re delighted. It"s rare to see a No. 1 playing a Masters 1000 in doubles." After a first round bye, Djokovic will open his Paris Masters singles campaign either against Italian Fabio Fognini or Marton Fucsovics from Hungary.