The Olympic champion, who won the 800 at the Glasgow Diamond League meeting earlier this month, qualified fastest for Wednesday's semi-finals in one minute 46.89 seconds.
"Today was all about qualifying, so I'm trying to reserve as much energy as possible," the Kenyan told reporters.
"I'm happy to be here at this time of the season, it is unbelievable, and my body is able to respond very quickly."
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After being plagued by a knee injury for most of 2013 and missing the world championships in Moscow, the 25-year-old was competing in only his fifth race of the season.
Rudisha clocked a season best time of 1:42.98 at the Diamond League meeting in Monaco on July 18 and looked relaxed as he led from the front and eased to an effortless heat victory on Tuesday.
"It has been a tough year, it has not been easy," he said. "I am going to struggle a bit this season, but I am forecasting to do well next year."
The men's 800 final is on Thursday.
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