Nick Kyrgios, Davis Cup
Tennis - Davis Cup Quarter-Finals - Australia v USA - Pat Rafter Arena, Brisbane, Australia - 9/4/17 Australia's Nick Kyrgios reacts in front of Jim Courier, team Captain for the USA, during his Davis Cup quarter-final match against Sam Querrey of the USA. Reuters / Steve Holland

Australian tennis star Nick Kyrgios has pulled out of the Millennium Estoril Open in Portugal and will fly back to Canberra for his grandfather's funeral. Kyrgios, the World No. 16, was hoping to begin his European clay-court season in Portugal before ATP World Tour Masters 1000 tournaments such as the Madrid Open (May 7-14) and the Italian Open (May 14-21) precede the French Open (May 22-June 11).

According to The Herlad Sun, Kyrgios will likely rejoin the European clay-court season in the lead-up to the French Open. “I just want to take the opportunity to let you all know, especially the people of Estoril and Cascais know, that I have unfortunately withdrawn from Millenium Estoril Open to go back to Australia and attend my grandfather’s funeral.

“It’s no secret that Estoril has been a very special stop for me on the ATP World Tour, so the decision was a hard one but my family is very important to me and I feel I need to be around my loved ones at this time as well as pay respects to my Papou, who I loved very much. I hope you can all understand and respect my decision," Kyrgios wrote on his Twitter feed.

Kyrgios has made a spectacular comeback since his second-round loss at the Australian Open in January. The 21-year-old was met with thunderous boos by his home fans at Melbourne Park for his in-game antics. Since then, Kyrgios has kept his emotions in check, beating World No. 2 Novak Djokovic on two separate occasions besides pushing Roger Federer to a classic five-set contest in the semi-final of the Miami Open at Key Biscayne, Florida. The young Aussie followed that up by leading his country past USA in the Davis Cup quarterfinal.

Though Nick Kyrgios isn't viewed as a legitimate threat to Rafael Nadal and Novak Djokovic on clay-court surfaces, several analysts expect him to make some noise at the Wimbledon and US Open later this year.