Seen as one of the trailblazers for Kenyan athletics and still closely involved with its development, the 72-year-old Keino said the country's haul of two golds compared with the 12 targeted was also due to runners racing too many events in the run-up to the Games.
Lessons should be learned and the same mistakes avoided in the future, added Keino, who won 1,500 metres gold in Mexico City in 1968 and the 3,000 metres steeplechase title in Munich four years later.
"When we had the trials we selected the best team," Keino, a Nandi tribesman whose full name is Hezekiah Kipchoge Keino, said at a news conference at the IAAF centenary celebrations in Barcelona.
"The athletes should have come to London at least 10 days before the Games and many only got in three of four days before," he added.
"The body has to adjust and acclimatise and the timing was not the right timing.
"When it comes to the Olympics you should not be competing in other events.
"Their performances were not at the level they did before the Games and this is a lesson for the runners, the federation, the coaches and the agents."
While David Rudisha's gold and world record in the 800 metres was the highlight of the Games for many, Kenya fell well short of the 36 medals overall they were targeting.
Men's marathon favourite Wilson Kiprotich could only manage bronze, while on the women's side Vivian Cheruiyot failed in her bid to match the 5,000-10,000 metres double she achieved at last year's world championships, finishing second in the 5,000 and third in the 10,000.
Ezekiel Kemboi won gold in the men's steeplechase.
The East African nation enjoyed its best showing at an Olympics four years ago in Beijing with all of their 16 medals coming on the track, six of them gold.
Keino said athletes should cut the number of meetings they competed in during an Olympic year and training methods needed to be overhauled.
"We need to put our heads together with Athletics Kenya and plan for future events," he said.
"We have a lot of talent. Let us forget about London, let us think about the next four years.
"If we sit together with those people we will be able to improve. Some of it is scientific training, some of it is mental training. Those are the most important in the world today.
"We have to work hard all the time and think for yourself and also for your country.”
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- Athletics, Track & Field