Barcelona have confirmed that midfielder may miss the rest of the season having ruptured a knee ligament in a nasty tackle against Roma on Wednesday.

The 22-year-old had been on the field a matter of minutes, after coming on as a second-half substitute in the 1-1 draw in Champions League Group E, when he suffered the injury in a challenge by Roma's Radja Nainggolan.

Manchester City manager Manuel Pellegrini said his team would have to improve the efficiency of their finishing after a 2-1 home defeat by Juventus in their Champions League opener.

City created more clear-cut chances than Juventus and took a 57th-minute lead through Giorgio Chiellini's own goal, only for clinical late strikes by Mario Mandzukic and Alvaro Morata to earn the visitors victory.

Five things to watch at this week's Formula One Singapore Grand Prix:

Zamalek outclassed South African visitors Orlando Pirates 4-1 on Sunday to keep alive hopes of a dream all-Egyptian CAF Confederation Cup final against title-holders Al-Ahly. 

Ahmed Tawfik, Ahmed Mekki, Mostafa Fathy and Kahraba scored for the White Knights, who led 2-1 at half-time in a Cairo match played behind closed doors for security reasons. 

Struggling Marseille secured a vital three points on Sunday as they thrashed Mediterranean rivals Bastia 4-1, while Rennes climbed up to second in Ligue 1 after beating nine-man Nantes 2-0.

A turbulent first month of the season had left Marseille with just three points from four matches and one place above the relegation zone prior to kick-off at the Stade Velodrome. 

Novak Djokovic captured his 10th Grand Slam title Sunday at the US Open after Roger Federer once more pushed the world number one him to his highest level.

The 28-year-old Serbian star defeated 17-time Grand Slam champion Federer 6-4, 5-7, 6-4, 6-4 in the final at Arthur Ashe Stadium, pulling level at 21-21 in the greatest current rivalry in tennis.

France's Sebastien Ogier clinched his third World Rally Championship in a row on Sunday by winning Rally Australia for the third year running, taking the 2015 title with three events remaining.

Ogier had a .03-second lead over Northern Ireland's Kris Meeke to begin Sunday's final five stages, and won the opening speed stage by 2.5 seconds.

Flavia Pennetta captured her first Grand Slam singles title at the US Open on Saturday and said she was happy to head into retirement.

The 33-year-old beat fellow Italian Roberta Vinci 7-6 (7/4), 6-2 to become the oldest first time women's winner at a major.

Frenchmen Nicolas Mahut and Pierre-Hugues Herbert won the US Open men's doubles crown on Saturday with a 6-4, 6-4 victory over Britain's Jamie Murray and Australian John Peers.

Mahut and Herbert became the first all-French duo to capture a US Open men's doubles title. It was also their first Grand Slam men's doubles crown.

Paris has officially declared itself a candidate to host the 2024 Olympic Games by submitting its letter of intention to the International Olympic Committee on Saturday, the Olympic Ambition Association (AAO) announced.

"The Olympic spirit and the city of Paris share a common attachment to unity in diversity, tolerance in the face of differences and the same belief in peace of openness," the letter, addressed to IOC president Thomas Bach and signed jointly by French National Olympic Committee president  Denis Masseglia, and Paris mayor Anne Hidalgo, explained.