NASCAR to require baseline concussion testing for drivers next season NASCAR will require baseline concussion testing for its drivers starting next season. NASCAR had only recommended the testing this season, but indicated to drivers that a preseason baseline screening could become mandatory as early as 2014. The baseline test will be compared with test results taken after a driver has crashed to help diagnose a concussion. "NASCAR made this decision because we think it is important to drivers' health for doctors to have the best information and tools available in evaluating injuries," said Steve O'Donnell, NASCAR vice president of racing operations. Drivers were informed of the mandate during a Thursday meeting at the R&D Center in Concord, N.C., with top NASCAR officials that lasted nearly two hours and covered a variety of topics concerning 2014 changes. The baseline testing will be performed through the widely used neurocognitive assessment ImPACT test, which evaluates an athlete's verbal and visual memory, processing speed and reaction time. O'Donnell said in February that NASCAR had identified 32 concussions in its top three national series since 2004, including three in 2012. One suffered by Dale Earnhardt Jr. forced NASCAR concussions into the spotlight. Earnhardt was injured in a crash during an August 2012 tire test at Kansas, but didn't seek treatment for a mild concussion. His stubborn streak instead kept him behind the wheel, and he was then part of a 25-car pileup in October at Talladega that triggered lingering headaches and other recognizable warning signs. Earnhardt went to a doctor, and he was ultimately benched for two races. NASCAR told competitors it is considering eliminating single-car qualifying next season in an overhaul that would likely implement road course-style qualifying at all but two tracks. Series officials outlined potential changes to qualifying procedures everywhere except Daytona and Talladega. NASCAR spokesman Kerry Tharp said the field would likely be set at Daytona and Talladega with an "open qualifying session" that would allow for a 60-minute drafting session. Top-ranked Serena Williams advanced to the semifinals of the WTA Championships by sweeping Petra Kvitova, 6-2, 6-3, in Istanbul, Turkey. Williams, the defending champion, won all three matches in her group without dropping a set. She's bidding for her fourth title in the eight-women, season-ending tournament. Li Na outlasted Jelena Jankovic, 6-3, 2-6, 6-3, for her second victory and eight-seeded Angelique Kerber upset No. 3 Agnieszka Radwanska, 6-2, 6-2, to remain in contention for the semifinals. Radwanska was eliminated. Kerber (1-1) went 0-3 last year in the tournament. She will play Kvitova on Friday for a spot in the last four. Top-seeded Juan Martin del Potro of Argentina eased past Marcos Baghdatis of Cyprus, 6-1, 6-2, to reach the quarterfinals of the Swiss Indoors at Basel. Del Potro will face Paul-Henri Mathieu of France, who beat compatriot Michael Llodra, 6-4, 6-3. Five-time Basel champion Roger Federer is in the other half of the draw, and will face Grigor Dimitrov of Bulgaria on Friday.