Former Japan national defender Naoki Matsuda is still unconscious one day after he suffered a cardiac arrest during training.

Matsuda collapsed Tuesday after finishing a 15-minute warmup run during training for J-League club Matsumoto Yamaga, and was rushed to a hospital. Team officials said Wednesday that he remains unconscious and is in serious condition.

The 34-year-old Matsuda played 40 times for Japan, including at the 2002 World Cup in Japan and South Korea. He played a total of 385 J-League games for the Yokohama F Marinos from 1995 to 2010.