The safety of Wimbledon’s grass courts has come into question after tennis superstar Serena Williams and France’s Adrian Mannarino were forced to withdraw from the tournament after suffering injuries. Some big names, including Roger Federer, say the courts are a “tad more slippery” than in recent years, but the slippery grass courts aren’t unusual and take a few matches for the players to wear the grass down, others say. The All England Club said maintenance of the courts hadn’t changed this year, but there have been wetter-than-usual conditions leading up to Wimbledon. Nick Kyrgios is another to dramatically fall as he finished off his match with 21st-seeded Frenchman Ugo Humbert. The Aussie won in 5 sets – “not too bad for a part-time player,” he said.