Japan midfielder Shinji Kagawa faces an anxious wait to discover the extent of the knee injury he suffered in Manchester United's 3-2 Champions League win over Braga on Tuesday.

Kagawa twisted his knee midway through the first half at Old Trafford, but played on until half-time before being replaced by Portugal winger Nani.

Usain Bolt, the world record-holder at 100 and 200 meters, said Tuesday he likes his chances at starting up a football career after he retires from athletics after the 2016 Rio de Janeiro Olympics.

"I would love to play," Bolt said. "I've played football. I've played charity matches. Something I really want to try.

French tennis star Jo-Wilfried Tsonga's hopes of making the end of season ATP Masters finals suffered a blow on Tuesday as he was forced to withdraw from the Valencia Open with a back problem.

The 27-year-old, who presently occupies the eighth and last spot for the November 5-11 tournament, had called for the physiotherapist in only the second game of his first round match with Belgian Xavier Malisse.

Poland's Sports Minister Joanna Mucha has tendered her resignation, government spokesman Pawel Gras said Tuesday, amid a row over the Polish football team's rain-postponed World Cup qualifier against England.

"Madame Minister Mucha placed herself at the disposal of Prime Minister Donald Tusk on Monday," Gras said on his Twitter feed, after growing speculation she would step down.

Serena Williams overcame an injury scare here Tuesday during a winning start to her bid to cap a brilliant comeback season by regaining the WTA Championship title.

The Wimbledon, U.S. Open and Olympic champion appeared to pull a gluteal muscle attempting a retrieve in the first set but played through the discomfort to win 6-4, 6-1 against Angelique Kerber, a debutant in this elite eight event.

Spanish former world number one Juan Carlos Ferrero's stellar career ended on a flat note on Tuesday as he exited in the first round of the Valencia Open beaten 7-5, 6-3 by compatriot Nicolas Almagro.

Ferrero, 32 and winner of 16 singles titles including the 2003 French Open, was very emotional as he addressed the spectators for the final time.

Arsene Wenger has called on his Arsenal stars to deliver an immediate response to their shock defeat against Norwich when Schalke visit the Emirates Stadium in the Champions League on Wednesday.

Wenger's team are now 10 points behind Premier League leaders Chelsea after losing to previously winless Norwich for the first time in 20 years on Saturday.

Manchester City visit Ajax on Wednesday knowing that they can afford no further setbacks if they are to avoid a painful repeat of last season's Champions League group-phase exit.

Dealt another fiendish draw, City find themselves in third place in Group D after two matches, five points behind leaders Real Madrid and three points adrift of Borussia Dortmund.

Borussia Dortmund will need to check Real Madrid's early Champions League momentum when the top two in Group D face off on Wednesday with the Germans facing an injury crisis and poor form.

Security is an issue for the arrival of the Spanish giants in the wake of Saturday's riots in Dortmund before Schalke's victory in the Ruhr derby.

Germany coach Joachim Loew has admitted making mistakes during his team's 4-4 draw with Sweden in last week's World Cup qualifier after the Germans threw away a four-goal lead.

Germany were 4-0 up at Berlin's Olympic Stadium with more than an hour played before the hosts' defense folded in the final 30 minutes as Sweden roared back to claim a point last Tuesday.