By Gary Smith, World-Track
Bolt, who currently holds the world record in both the 100m and 200m, was phenomenal throughout the entire season last year – particularly in Beijing, where he set the world records on his way to winning the Olympic Games sprint double.
But even with those majestic performances, Greene, who himself was floating on top of the world during his time, still believes the Jamaican has not yet run a complete 100m race.
"No one knows how fast Usain Bolt can actually go," the American said in an interview with BBC Sports in Berlin. "I don’t think he ran a complete race in the 100m yet, so he hasn’t reached his top-end speed and that’s something everyone is looking to see."
Greene also thinks that Bolt, a 200m speciallist before his coach Glen Mills decided to go ahead on his promise to test him over the 100m two seasons ago – still doesn’t know exactly how to run the 100m, and is only learning with every race.
The American former Olympic and world champion believes also that Bolt ran no where close to his max this season, despite producing times of 9.79 over the 100m and 19.59 over the half-lap event.
"Since he started running the 100m he [hasn’t run a complete race] and he definitely hasn’t done it this season," Greene said. "I think he’s just been playing it easy, getting into races and just going out there and competing, but he definitely hasn’t reached his top yet.
"I can’t say Bolt is the complete package," Greene explains. "He really doesn’t know what he is doing, he is learning as he goes on.
"He hasn’t been a 100m runner…he’s only been running the race for two-years now so he still has a lot to learn."