Team Sky will enter the Volta ao Algarve with just seven riders after Michal Kwiatkowski's late withdrawal with a stomach bug.
The Pole, who finished second to new teammate Geraint Thomas in the Portuguese race last year, is the third Sky rider in recent days to be struck down with illness.
In Kwiatkowski's absence, Thomas will be a man short in his title defence, with Michal Golas, Sebastian Henao, David Lopez, Ian Stannard, Lars Petter Nordhaug and Salvatore Puccio for support.
Nicolas Roche has replaced Landa in the Ruta del Sol, where Sky will be led by Wout Poels - winner of the recent Volta a Valencia - who will be joined by Vasil Kiryienka, Christian Knees, Gianni Moscon, Ben Swift.
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