Robson initially worked well with the Croatian, rising to world number 38 in April, but she suffered six first-round defeats in 2013.
The Australian-born Briton made the decision before this week's Madrid Masters, where she defeated world number four Agnieszka Radwanska on Monday, her first victory against a top-five player.
The previous week she had suffered another first-round exit, to Ayumi Morita at the Portugal Open.
She will be coached by Dutchman Sven Groeneveld for now. He worked with Robson earlier in her career and is currently part of the Adidas team of coaches,
World number 41 Robson started working with Krajan after winning silver in the London 2012 Olympic doubles.
The Croat is known as a tough taskmaster who puts intense pressure on his charges, something which appeared to derail the 19-year-old Robson's natural, powerful game.
Robson's slump reached its nadir when she lost to world number 146 Paula Ormaechea in Britain's Fed Cup tie with Argentina, a match she had been expected to win.
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- Ayumi Morita