Michael Johnson has suggested that sprinter Justin Gatlin is unhappy with his portrayal as a villain of the sport.

The American, who has previously served two doping bans and was stripped of the Olympic gold he won in Athens in 2004, produced the fastest time of the 100m heats at the World Athletics Championships in Beijing.

However, Johnson is convinced that Gatlin's image as the bad boy of track and field may be fuelling the sprinter's performances this year.

He told BBC Sport: "Justin Gatlin has come here to run. I think he has a chip on his shoulder about being painted as the villain.

"He's brought that on himself, but he's come into this with a real chip on his shoulder, and it shows. It's benefiting him in terms of his performance. This aggressive approach that he has taken is working well for him."

Usain Bolt is also into the semi-finals after running 9.96s in the heats.