Furious Usain Bolt admitted he must improve his start as he plots a winning farewell at the World Championships.
The eight-time Olympic champion recovered from a bad start to win his 100 metres heat at the London Stadium on Friday ahead of Saturday's semi-final and final.
Bolt's victory came just before Sir Mo Farah raised the roof to defend his 10,000m title.
Bolt triumphed in 10.07 seconds in the stadium where he declared himself a "living legend" after retaining his 100m and 200m titles at the 2012 Olympics.
He will retire at the end of the championships following the 4x100m relay next weekend.
But he had to dig deep to power to victory in the second half of the race on the opening night and conceded he needed to resolve the issue he had with the blocks on Saturday.
"That was very bad," Bolt said.
"I stumbled coming out of the blocks. I'm not very fond of these blocks. I think these are the worst ones I've ever experienced. I have to get this start together because I can't keep doing this.
"It's shaky. When I did my warm-up it (the blocks) pushed back. It is just not what I am used to, not as sturdy or firm."
The Jamaican was welcomed to London by a raucous crowd who only got louder for Farah as he defended his 10,000m crown.
The four-time Olympic champion completed the first part of his double bid - which also includes the 5000m - as he aims to retire from the track this month.
"Yeah, I definitely agree with them, they know what they're doing," he said, after being told commentators Steve Cram and Brendan Foster said it was his greatest performance.
"It was one of the toughest races of my life. The guys gave it to me, it wasn't about Mo, it was about 'how do we beat Mo?'
"You had the Kenyans, the Ethiopians, the Ugandans, everybody working as a team against me. Fair play to them, they worked it hard and they chucked everything at me.
"I just had to stay strong, believe in myself and think, 'I didn't work for nothing, I'm not losing in my home town. I can't'."
Elsewhere, Laura Muir, Laura Weightman, Sarah McDonald and Jessica Judd reached the 1500m semi-final and Reece Prescod, CJ Ujah and James Dasaolu qualified for the 100m semi-final.
Holly Bradshaw made the pole vault final but Nick Percy missed out in the discus.