Beijing, Aug 27 (IANS): Usain Bolt's coach, Glen Mills, says the World sprint champion had not been at his best for the 100 metres earlier this week but the fact he managed to successfully defend his title was all that mattered.

The 28-year-old superstar clocked a season-best 9.79 seconds on Sunday to edge main rival Justin Gatlin of the United States, and retain the 100m title he won in Moscow two years ago, reports CMC.

For Bolt, the victory came against a run of several unconvincing performances - including the semi-final where he stumbled after leaving the blocks and was forced to make a miraculous recovery to win the race.

“That's not the best of Usain but I am completely satisfied with the result,” Mills said on Wednesday.

“This is the hardest of the titles that he has ever won. It was very challenging because of the challenges he had to face in preparation for Beijing and hats off to him for a real gutsy and champion-like performance.”

For the first time since he shot to global fame in 2008, Bolt entered a major championship as the underdog. His previous fastest time this year was 9.87 seconds compared to Gatlin's world-leading 9.74.

Gatlin also made a huge statement in the semi-finals, storming to 9.77 seconds but Mills labelled Bolt a "competitor and champion" who knew how to execute on the big day.

"He did more than enough to establish himself as the man to beat and it turned out exactly that. If we wanted to win we would have to beat Gatlin," Mills explained.

"Usain is a competitor and a champion, so getting him to be in the frame of mind wasn't difficult. This is the most difficult one, so we are happy that we were able to overcome."

Bolt and Gatlin will clash again when they meet in the final of the 200m on Thursday.