I do the below, but the centered=false attribute is being ignored. How to resolve this?

Code:
 xtype: 'button',
                    id: 'btnMyTickets',
                    cls: 'arrow',
                    baseCls: 'list-dashboard-button',
                    text: 'My Jobs',
                    centered: false,
                    handler: function ()
                    {
                       alert('hi');
                    }